Compare and Contrast each rhetorical situations

Assignment#1 Description: Exploratory Essay

Purpose: The exploratory essay is designed to introduce you to writing and research in your academic discipline and to emphasize the relevance of scholarship to our everyday lives. For this assignment you will need to select a popular media OR trade publication article AND an academic journal article reporting on the same/similar topic to compare and contrast in terms of their rhetorical situation and style.

Audience: A beginning college student/researcher in your discipline.

Process: This assignment requires you to complete the following steps:

Step 1. Find a popular media or trade publication article (print or online) focused on a topic pertaining to your academic discipline.

Step 2. Read the article and identify any possible keywords from it you can use to search for an academic journal article about the same topic. *Consult with your instructor if you think you need to find an academic journal article on a related topic because you are unable to find one about the same topic.

Step 3. Use the library resources, such as your subject guide, to find an academic journal article about the same topic as your popular media or trade publication article. Select an article published recently (within the last 5 years preferably, but no more than the last 10 years); you want to be aware of what your academic discipline is researching and writing about now.

Step 4. Read the academic journal article and popular media or trade publication article you selected in Step 1, analyzing them for rhetorical situation and style.

Step 5. Draft your essay, comparing and contrasting your two articles in terms of their purpose, content, and style. Refer to the handout “Article Analysis Guide” for detailed information about how to draft your essay.

Format: The exploratory essay should be approximately 3-4 typed and double-spaced pages (the required title page and bibliography page do not count toward this requirement), conform to formatting guidelines (12 pt. Times New Roman font, 1” margins, proper heading, etc.), and use APA style or the documentation style of your field.

Assessment: 10 % of your final course grade

Due Date: The rough draft is due —. The final draft is due —.

ACL REHAB (T SGROI AND J MOLONY, SECTION EDITORS)

ACL Rehabilitation Progression: Where Are We Now?

John T. Cavanaugh1 & Matthew Powers1

Published online: 8 August 2017
# Springer Science+Business Media, LLC 2017

Abstract
Purpose of Review With the increase of publications available
to the rehabilitation specialist, there is a need to identify a
progression to safely progress the patient through their post-
operative ACL reconstruction rehabilitation program.
Rehabilitation after ACL reconstruction should follow an
evidence-based functional progression with graded increase
in difficulty in activities.
Recent Findings Clinicians should be discouraged not to use
strict time frames and protocols when treating patients follow-
ing ACL reconstruction. Rather, guidelines should be follow-
ed that allow the rehabilitation specialists to progress the pa-
tient as improvements in strength, edema, proprioception,
pain, and range of motion are demonstrated. Prior to returning
to sport, specific objective quantitative and qualitative criteria
should be met. The time from surgery should not be the only
consideration.
Summary The rehabilitation specialist needs to take into ac-
count tissue healing, any concomitant procedures,
patellofemoral joint forces, and the goals of the patient in
crafting a structured rehabilitation program. Achieving sym-
metrical full knee extension, decreasing knee joint effusion,
and quadriceps activation early in the rehabilitation process
set the stage for a safe progression. Weight bearing is begun
immediately following surgery to promote knee extension and
hinder quadriceps inhibition. As the patient progresses
through their rehabilitative course, the rehabilitation specialist

should continually challenge the patient as is appropriate
based upon their goals, their levels of strength, amount of
healing, and the performance of the given task.

Keywords Knee . Cruciate . Rehabilitation . Progression .

Guideline . Criteria

Introduction

Over 200,000 anterior cruciate ligament (ACL) injuries occur
in the USA annually [1]. It is estimated that more than half of
these injuries undergo surgical reconstruction [2]. Following
ACL reconstruction (ACLR), under the direction of the ortho-
pedic surgeon, the rehabilitation specialist is charged with the
responsibility of returning the patient to their pre-injury level
of function. Post-operative rehabilitation programs have
changed dramatically over the past couple of decades. Strict
protocols based on time elapsed from surgery have been re-
placed by criteria based guidelines (Table 1). These guidelines
follow a progression where selective criteria are met prior to
advancement in the program. This paper will discuss the pro-
gression of rehabilitation following ACL reconstruction.

A functional progression was defined by Kegerreis [3] as
an ordered sequence of activities enabling the acquisition or
reacquisition of skills required for the safe and effective per-
formance of athletic endeavors. In other words, the patient
needs to master a simple activity before advancing to a more
demanding activity. Programs are individualized, where some
patients will be ready to advance sooner than others.
Biological factors such as graft revascularization and matura-
tion as well as fixation techniques are also considered to en-
sure a safe progression through the ACLR rehabilitation
program.

This article is part of the Topical Collection on ACL Rehab

* John T. Cavanaugh
cavanaughj@hss.edu

1 Sports Rehabilitation & Performance Center, Hospital For Special
Surgery, 535 East 70th Street, New York, NY 10021, USA

Curr Rev Musculoskelet Med (2017) 10:289–296
DOI 10.1007/s12178-017-9426-3

mailto:cavanaughj@hss.edu

http://crossmark.crossref.org/dialog/?doi=10.1007/s12178-017-9426-3&domain=pdf

Table 1 Anterior cruciate ligament (BTB) rehabilitation guideline

Post-operative phase I (weeks 0–2)
Goals:
▪ Emphasis on full passive extension
▪ Control post-operative pain/swelling
▪ Range of motion 0° → 90°
▪ Early progressive weight bearing
▪ Prevent quadriceps inhibition
▪ Independence in home therapeutic exercise program

Precautions:
▪ Avoid active knee extension 40° → 0°
▪ Avoid ambulation without brace locked at 0°
▪ Avoid heat application
▪ Avoid prolonged standing/walking

Treatment strategies:
▪ Towel extensions, prone hangs, etc.
▪ Quadriceps re-education (quad sets with EMS or EMG)
▪ Progressive weight bearing
▪ PWB → WBAT (patella tendon) with brace locked at 0° with crutches
▪ Patella mobilization
▪ Active flexion/active-assisted extension 90° → 0° exercise
▪ SLR’s (all planes)
▪ Brace locked at 0° for SLR (supine)
▪ Short crank ergometry
▪ Hip progressive resisted exercises
▪ Proprioception board/balance system (bilateral weight bearing)
▪ Leg press (bilateral/80° → 5° arc) (if ROM >90°)
▪ Upper extremity cardiovascular exercises as tolerated
▪ Cryotherapy
▪ Home therapeutic exercise program: evaluation based
▪ Emphasize patient compliance to home therapeutic exercise program
and weight bearing precautions/progression

Criteria for advancement:
▪ Ability to SLR without quadricep lag
▪ ROM 0° → 90°
▪ Demonstrate ability to unilateral (involved extremity) weight bear
without pain

Post-operative phase 2 (weeks 2–6)
Goals:
▪ ROM 0° → 130°
▪ Good patella mobility
▪ Minimal swelling
▪ Restore normal gait (non-antalgic)
▪ Ascend 8″ stairs with good control without pain

Precautions:
▪ Avoid descending stairs reciprocally until adequate quadriceps control
and lower extremity alignment

▪ Avoid pain with therapeutic exercise and functional activities
Treatment strategies:
▪ Progressive weight bearing/WBAT (patella tendon) with crutches brace
opened 0° → 50°, if good quadriceps control (good quad set/ability to
SLR without lag or pain)

▪ D/C crutches when gait is non-antalgic
▪ Brace changed to MD preference (OTS brace, patella sleeve, etc.)
▪ Standard ergometry (if knee ROM >115°)
▪ Leg press (90° → 0° arc)
▪ AAROM exercises
▪ Mini squats/weight shifts
▪ Proprioception training: prop board/balance system/contralateral
Theraband exercises

▪ Initiate forward step-up program
▪ Stairmaster
▪ Aquaciser (gait training) if incision benign
▪ SLR’s (progressive resistance)
▪ Hamstring/calf flexibility exercises
▪ Hip/hamstring PRE
▪ Core stabilization exercises
▪ Retrograde incline treadmill ambulation
▪ Active knee extension to 40°
▪ Home therapeutic exercise program: Individualized

Criteria for advancement:
▪ ROM 0° → 125°

Table 1 (continued)

▪ Normal gait pattern
▪ Demonstrate ability to ascend 8″ step
▪ Good patella mobility

Post-operative phase 3 (weeks 6–14)
Goals:
▪ Restore Full ROM
▪ Demonstrate ability to descend 8″ stairs with good leg control

without pain
▪ Improve ADL endurance
▪ Improve lower extremity flexibility
▪ Protect patellofemoral joint

Precautions:
▪ Avoid pain with therapeutic exercise and functional activities
▪ Avoid running and sport activity till adequate strength development

and MD clearance
Treatment strategies:
▪ Progress squat program
▪ Initiate step down program
▪ Leg press
▪ Lunges
▪ Isometric → isotonic knee extensions 90°→40°
▪ Advanced proprioception training (perturbations)
▪ Agility exercises (sport cord)
▪ Retrograde treadmill ambulation/running
▪ Quadriceps stretching
▪ KT 1000 knee ligament arthrometer exam at 3months
▪ Home therapeutic exercise program: evaluation based

Criteria for advancement:
▪ ROM to WNL
▪ Ability to descend 8″ stairs with good leg control/alignment

without pain
▪ Functional progression pending KT1000 and functional

assessment
Post-operative phase 4 (weeks 14–22)
Goals:
▪ Demonstrate ability to run pain free
▪ Maximize strength and flexibility as to meet demands of activities

of daily living
▪ Isokinetic test ≥85% limb symmetry

Precautions:
▪ Avoid pain with therapeutic exercise and functional activities
▪ Avoid sport activity till adequate strength development and MD

clearance
Treatment strategies:
▪ Start forward running (treadmill) program when 8″ step down

satisfactory
▪ Continue LE strengthening and flexibility programs
▪ Advance agility program/sport specific
▪ Start plyometric program when strength base sufficient
▪ Isotonic knee extension (full arc/pain and crepitus free)
▪ Isokinetic training (fast → moderate velocities)
▪ Home therapeutic exercise program: Individualized

Criteria for advancement:
▪ Symptom-free running
▪ Isokinetic test ≥85% limb symmetry
▪ Lack of apprehension with plyometric and agility activities to date

Post-operative phase 5—return to sport (weeks 22–?)
Goals:
▪ Lack of apprehension with sport specific movements
▪ Maximize strength and flexibility as to meet demands of

individual’s sport activity
▪ Isokinetic test ≥90% limb symmetry
▪ Hop test ≥90% limb symmetry
▪ Acceptable quality movement assessment

290 Curr Rev Musculoskelet Med (2017) 10:289–296

Range of Motion

Following ACLR, achieving full knee extension range of mo-
tion (ROM) should be achieved as soon as possible. Extension
loss results in abnormal joint arthrokinematics at both the
tibiofemoral and patellofemoral joints. This in turn leads to
abnormal articular cartilage contact pressures and quadriceps
inhibition [4, 5•, 6].

Achieving full extension should ideally be achieved preop-
eratively. McHugh, et al. [7] found that patients with knee
extension loss were 5× more likely to have extension loss
issues after surgery.

Treatment strategies employed to achieve full extension
include low load prolonged stretching (Fig. 1) and calf

stretching. Patellofemoral joint mobilizations in a superior di-
rection are utilized to encourage extension ROM [8] Sleeping
in a post-operative brace locked at 0° extension is utilized to
encourage extension and discourage the formation of a flexion
contracture during the night hours. Full extension is one of
several important criteria to meet to safely progress the patient
off their crutches after surgery.

ROM exercises to facilitate flexion begin immediately after
ACLR. ROM flexion goals of 120° should be met 4 weeks
following surgery and full symmetrical flexion achieved by
12 weeks. Treatment strategies begin with active-assisted
ROM exercises off the side of a plinth or bed (Fig. 2).
Treatment strategies employed to further progress gains in
flexion ROM include wall slides, active-assisted ROM sitting
or on a step, and one half moon movement on a stationary
bicycle. A short crank ergometer (Fig. 3) is utilized allowing
patients to cycle earlier in the rehabilitative process and thus
facilitate gains in flexion ROM [9]. Fleming and colleagues
[10] demonstrated relatively low ACL peak strain values
in vivo during stationary cycling.

Table 1 (continued)
Precautions:
▪ Avoid pain with therapeutic exercise and functional activities
▪ Avoid sport activity till adequate strength development and MD

clearance
Treatment strategies:
▪ Continue to advance LE strengthening, flexibility, and agility

programs
▪ Advance plyometric program
▪ Brace for sport activity (MD preference)
▪ Monitor patient’s activity level throughout course of rehabilitation
▪ Reassess patient’s complaint’s (i.e., pain/swelling daily—adjust

program accordingly)
▪ Encourage compliance to home therapeutic exercise program
▪ KT 1000 knee ligament arthrometer exam, isokinetic test, hop

test(s), quality movement assessment at 6months
▪ Home therapeutic exercise program: Individualized

Criteria for discharge:
▪ Isokinetic and functional hop test(s)≥90% limb symmetry
▪ Acceptable quality movement assessment
▪ Lack of apprehension with sport specific movements
▪ Flexibility to accepted levels of sport performance
▪ Independence with gym program for maintenance and progression

of therapeutic exercise program at discharge

Adapted from “Anterior Cruciate Ligament Reconstruction” Cavanaugh
JT, Postsurgical Rehabilitation Guidelines for the Orthopedic Clinician
Cioppa-Mosca J, Cahill JB, Cavanaugh JT, Corradi-Scalise D, Rudnick
H, Wollf AL, (eds) Elsevier Publishers pp.425–438, 2006

Fig. 1 Passive low load prolonged stretching utilizing a rolled towel
under the ankle

Fig. 2 Active-assisted knee flexion/extension

Fig. 3 Short crank bicycle

Curr Rev Musculoskelet Med (2017) 10:289–296 291

Inferior-guided patellofemoral joint mobilizations are uti-
lized to encourage gains in knee flexion [8]. When 120° of
knee flexion is demonstrated, quadriceps stretching off the
side of a plinth (Fig. 4) and eventually in a prone position is
introduced to the patient’s program. Soft tissue massage can
be of particular benefit throughout the progression to restore
full symmetrical flexion ROM.

Post-operative Weight Bearing

Weight bearing progression following ACLR is dictated by
graft selection and surgeon preference. Advanced fixation
techniques such as cancellous screw bone-to-bone fixation
allow for immediate post-operative weight bearing.
Following ACLR with an autologous bone-patellar tendon-
bone (BTB) graft weight bearing is at first partial (50%) uti-
lizing crutches and subsequently progressed to weight bearing
as tolerated (WBAT) on successive days. This progression
allows the knee joint to acclimate to increased loads.
Ambulating in water, e.g., underwater treadmill (Fig. 5) can
be utilized to gradually apply increased load through the knee
joint and assist in the development of a normal gait pattern.
Walking in chest-deep water results in a 60 to 75% reduction
in weight bearing, while walking in waist-deep water results in
a 40 to 50% reduction in weight bearing [11, 12].

A post-operative brace is initially locked at 0° for ambula-
tion to protect the harvest site. The brace is opened when
quadriceps control is demonstrated by the ability of the patient
to straight leg raise (SLR) without a quadriceps lag or com-
plaints of pain. Crutches are then discontinued upon meeting
the criteria of demonstrating a normal non-antalgic gait.

A significant decrease in patellofemoral pain has been re-
ported when an immediate progressive weight bearing guide-
line is utilized [13•]. ACLR’s utilizing hamstring or allografts
are progressed at a slower rate secondary to the decreased
strength of soft tissue fixation and biological considerations,
respectively. Weight bearing may be delayed following
ACLR’s with concomitant articular cartilage or meniscus re-
pair procedures.

Strengthening

Re-establishing quadriceps control is an early goal of post-
operative ACLR rehabilitation. Controlling post-operative ef-
fusion assists in discouraging quadriceps inhibition. Spencer
et al. [14] identified that mechanoreceptors in the joint capsule
respond to changes in tension and in turn inhibit motor nerves
supplying the quadriceps muscles. Therapeutic interventions
utilized include the use a commercial cold with compression
device (Fig. 6), quadriceps setting with a towel under the knee,
and weight bearing with the appropriate amount of load.
Should a patient have difficulty eliciting a quadriceps contrac-
tion, a biofeedback unit or an electrical muscle stimulator can
be used in conjunction with the quadriceps setting exercise to

Fig. 4 Quadricep stretching off the side of a plinth

Fig. 5 Underwater treadmill (Hudson Aquatic Systems LLC, Angola,
IN)

Fig. 6 Gameready cold/compression device

292 Curr Rev Musculoskelet Med (2017) 10:289–296

better facilitate a quadriceps contraction. Numerous studies
[15–17] have demonstrated an earlier return of quadriceps
strength after ACLR with the use of electrical stimulation.
As quadriceps activation is demonstrated, a key observation
in order to progress the patient is seeing the patient perform a
straight leg raise without the assistance of the post-operative
brace without any complaints of pain or quadriceps lag. When
this criteria is met, the post-operative brace can be opened to
allow normal knee range of motion during ambulation.
Crutches are continued at this point until a non-antalgic gait
is demonstrated. Closed kinetic chain exercises including leg
press and squats inside a pain free arc of motion are introduced
as these activities have been shown to minimize stress to the
ACL [18–21, 22•, 23]. Limited evidence now demonstrates
that open kinetic chain (OKC) exercises inside a 90°–0° arc of
motion may not compromise graft laxity.[24–26]. Mikkelsen
et al., randomized 44 ACLR (BTB) patients to either a closed
chain rehabilitation only program and a closed chain program
that added open chain exercises 6 weeks post-operatively. At
6-month follow up, KT-1000 knee ligament arthrometer
values showed no significant difference in knee laxity be-
tween the groups. A significant increase in quadriceps
strength in the open chain group was also identified. With
the demonstration of 0°–130° ROM, OKC exercise progres-
sion begins with multiangle quadriceps isometrics inside a
90°–40° arc of motion (Fig. 7). Isometric exercises are
progressed to isotonic exercises using progressive resistance
(PRE). At 3 months, post-operatively isotonic exercise is
allowed throughout a full arc of motion and progressed to
isokinetic exercises utilizing moderate-fast speeds.
Throughout this progression, the rehabilitation specialist
should closely monitor the patellofemoral joint for crepitus
and complaints of pain.

Neuromuscular Training

After ACLR, surgery afferent information is altered, which
results in a disruption in the pathway between the patient’s
center of gravity and base of support [27]. Improving neuro-
muscular reaction time to imposed loads enhances dynamic
stabilization around the knee and thus protects the static re-
constructed tissue from overstress or re-injury [28]. As soon as
the patient achieves 50% weight bearing, neuromuscular/
balance training is initiated on a dynamic balance system
(Fig. 8) or proprioception device (foam cushion, rocker board,
etc.). Balance activities are then increased progressively to
include unilateral weight bearing, use of multiplanar support
surfaces, and perturbation training [29]. Activities should at-
tempt to eliminate or alter sensory information from the visual,
vestibular, and somatosensory systems so as to challenge the
other systems.

Continued Progression

As range of motion and strength is demonstrated, the patient is
instructed in a progressive step-up program, first mastering 6″
steps advancing to normal stair height 8″ steps. As further
strength is demonstrated, a forward step down program is
introduced (Fig. 9).

Fig. 7 Isometric Knee Extension at 60° knee flexion Fig. 8 Dynamic balance system (Biodex Corporation, Shirley, NY)

Curr Rev Musculoskelet Med (2017) 10:289–296 293

After 3 months post-op, if ROM is within normal limits and
sufficient strength is demonstrated via a pain-free 8″ step down
without deviation, a running program is started. Backward run-
ning is preceded by forward running, as retrograde running has
been shown to generate lower patellofemoral joint compression
forces than forward running [30]. An Alter G treadmill (Alter G,
Inc., Fremont, CA) (Fig. 10) is utilized to incrementally add load
during a forward running progression. A running program is
progressed with an emphasis on speed over shorter distances
vs. slower distance running.

Plyometric training is then incorporated only if full ROM, an
adequate strength base and flexibility, is demonstrated.
Plyometric training should follow a progression with its compo-
nents of speed, intensity, load, volume, and frequency being
monitored and progressed accordingly. Activities should begin
with simple drills and advance to more complex exercises (e.g.,
double leg jumping vs. box drills). Agility and deceleratory train-
ing are important interventions to include in the later phases of
rehabilitation in preparation for return to sport.

Return to Sport

When to return to sport following ACLR is a controversial
issue. Pinczewski et al. [31] reported that one in four patients
undergoing an ACLR will suffer a second tear within 10 years
of their first. Paterno et al. [32•] reported an incidence rate of a
second ACL injury within 2 years after returning to sports was
nearly 6× greater then healthy controls.

More and more surgeons and rehabilitation specialists are
utilizing numerous forms of assessment in determining an
athlete’s readiness to return to play. Subjective rating scales,
knee laxity testing, isokinetic testing, functional hop testing,
balance testing, and qualitative movement assessment
(Fig. 11) are utilized to provide evidence in the decision mak-
ing process. Acceptable scores on these assessments are re-
quired to safely return the athlete to sport. Following dis-
charge from a formal rehabilitation program, volume of ath-
letic exposures needs to be modified.

Several studies have demonstrated deficits in muscular
strength, kinesthetic sense, balance, and force attenuation
6 months to 2 years following reconstruction [32•, 33–35].
Return to sport 6 months following ACLR, therefore is no longer
the expected norm.

Fig. 10 Unweighted treadmill (AlterG Inc., Fremont, CA)

Fig. 9 Forward step down exercise off an 8″ step

Fig. 11 Quality movement assessment of a single leg squat exercise

294 Curr Rev Musculoskelet Med (2017) 10:289–296

Summary

Rehabilitation following ACL reconstruction has shifted from a
paradigm based on protocols to a progression based program with
gradient increases in difficulty. It is the rehabilitation specialist’s
responsibility to consider the forces placed on the healing ACL
graft and patellofemoral contact pressures generated during spe-
cific exercises and activities. Early in the rehabilitative process,
the focus needs to be on gaining full knee extension, decreasing
edema, and developing quadriceps strength. Therapeutic exer-
cises should progress in difficulty often being performed in a
variety of positions and settings. Neuromuscular training should
be implemented into the rehabilitation program as early as
deemed appropriate and progressed accordingly throughout the
rehabilitative process. ACLR rehabilitation progression should be
based on objective criteria and not just time frames. In order to
achieve a successful outcome the rehabilitation specialist must
continually assess the patient and select exercises that challenge
the patient properly. When the patient is ready to return to sports,
objective criteria must be met in order to reduce the risk of further
injury. This transition is now considered to take place at greater
than 6 months. Exposure/volume to athletic activity needs to be
controlled in the post-rehabilitation period.

Compliance with Ethical Standards

Conflict of Interest Both authors declare that they have no conflict of
interest.

Human and Animal Rights and Informed Consent This article does
not contain any studies with human or animal subjects performed by any of
the authors. Additional informed consent was obtained from all individual
participants for whom identifying information is included in this article.

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1567–73. Study looks at the risk on further injury to both the
ipsilateral and contralateral knees for up to 2 years following
ACL reconstruction.

33. Decker MJ, Torry MR, Noonan TH, Sterett WI, Steadman JR. Gait
retraining after anterior cruciate ligament reconstruction. Arch Phys
Med Rehabil. 2004;85(5):848–56.

34. Ernst GP, Saliba E, Diduch DR, Hurwitz SR, Ball DW. Lower
extremity compensations following anterior cruciate ligament re-
construction. Phys Ther. 2000;80(3):251–60.

35. Mattacola CG, Perrin DH, Gansneder BM, Gieck JH, Saliba EN,
McCue FC 3rd. Strength, functional outcome, and postural stability
after anterior cruciate ligament reconstruction. J Athl Train.
2002;37(3):262–8.

296 Curr Rev Musculoskelet Med (2017) 10:289–296

ACL Rehabilitation Progression: Where Are We Now?
Abstract
Abstract
Abstract
Abstract
Introduction
Range of Motion
Post-operative Weight Bearing
Strengthening
Neuromuscular Training
Continued Progression
Return to Sport
Summary
References
Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance

Current Concepts for Injury Prevention
in Athletes After Anterior Cruciate
Ligament Reconstruction

Timothy E. Hewett,*yz§ PhD, FACSM, Stephanie L. Di Stasi,yz PhD, PT,
and Gregory D. Myer,y§||{# PhD, FACSM, CSCS*D
Investigation performed at The Sports Health and Performance Institute, The Ohio State
University

Ligament reconstruction is the current standard of care for active patients with an anterior cruciate ligament (ACL) rupture.
Although the majority of ACL reconstruction (ACLR) surgeries successfully restore the mechanical stability of the injured knee,
postsurgical outcomes remain widely varied. Less than half of athletes who undergo ACLR return to sport within the first year
after surgery, and it is estimated that approximately 1 in 4 to 1 in 5 young, active athletes who undergo ACLR will go on to a sec-
ond knee injury. The outcomes after a second knee injury and surgery are significantly less favorable than outcomes after primary
injuries. As advances in graft reconstruction and fixation techniques have improved to consistently restore passive joint stability to
the preinjury level, successful return to sport after ACLR appears to be predicated on numerous postsurgical factors. Importantly,
a secondary ACL injury is most strongly related to modifiable postsurgical risk factors. Biomechanical abnormalities and move-
ment asymmetries, which are more prevalent in this cohort than previously hypothesized, can persist despite high levels of func-
tional performance, and also represent biomechanical and neuromuscular control deficits and imbalances that are strongly
associated with secondary injury incidence. Decreased neuromuscular control and high-risk movement biomechanics, which
appear to be heavily influenced by abnormal trunk and lower extremity movement patterns, not only predict first knee injury
risk but also reinjury risk. These seminal findings indicate that abnormal movement biomechanics and neuromuscular control pro-
files are likely both residual to, and exacerbated by, the initial injury. Evidence-based medicine (EBM) strategies should be used to
develop effective, efficacious interventions targeted to these impairments to optimize the safe return to high-risk activity.

In this Current Concepts article, the authors present the latest evidence related to risk factors associated with ligament failure or
a secondary (contralateral) injury in athletes who return to sport after ACLR. From these data, they propose an EBM paradigm
shift in postoperative rehabilitation and return-to-sport training after ACLR that is focused on the resolution of neuromuscular def-
icits that commonly persist after surgical reconstruction and standard rehabilitation of athletes.

Keywords: anterior cruciate ligament; anterior cruciate ligament reconstruction; second injury; ACL risk factors; ACL injury
prevention

Anterior cruciate ligament (ACL) injuries affect more than
120,000 athletes in the United States every year28,49 and
are 1 of the most common and devastating knee injuries
sustained as a result of sports participation. Anterior cru-
ciate ligament injuries often result in joint effusion, muscle
weakness, altered movement, and reduced functional per-
formance; few athletes are able to resume sports at the
same level without surgery.14 Anterior cruciate ligament
reconstruction (ACLR) continues to be the standard of
care for ACL-deficient athletes who aim to return to
high-level sporting activities,50 but outcomes are widely
varied10,20,31,35 and unexpectedly poorer than previously
reported.3,20,35 Less than half of athletes who undergo
reconstruction are able to return to sport within the first
year after surgery.3 For those athletes who successfully

return to activity, it is estimated that approximately 1 in
4 will go on to a second knee injury.39,47,74,81 Expectedly,
the outcomes after a second ACL injury and subsequent
ligament reconstruction are notably less favorable.84

Deficits in neuromuscular control during dynamic move-
ments are hypothesized to be the principal culprit in both
primary37,78,94,95 and secondary ACL injury risk.74,86 Exces-
sive out-of-plane knee loads, particularly increased external
knee abduction moments, predict principal ACL injury inci-
dence in young female athletes with high specificity and
sensitivity.37 Frontal-plane displacement of the trunk94 as
well as reduced core proprioception95 are both predictive
of a primary ACL injury in female athletes.37 Five-year
follow-up with this cohort indicated that 44% of ACL-
injured patients went on to a secondary ACL injury. Injury
risk in athletic populations appears not to be limited to
frontal-plane mechanisms alone; athletes who went on to
a primary ACL injury also demonstrated significant side-
to-side differences in lower extremity biomechanics as well
as reduced relative lower extremity flexor activation

M

The American Journal of Sports Medicine, Vol. 41, No. 1
DOI: 10.1177/0363546512459638
� 2013 The Author(s)

216

Clinical Sports Medicine Update

http://crossmark.crossref.org/dialog/?doi=10.1177%2F0363546512459638&domain=pdf&date_stamp=2012-10-05

relative to uninjured controls during the drop vertical
jump.37 Similar mechanisms of injury risk have been identi-
fied in athletes medically cleared to return to sport after
ACLR.74 Findings from a population of young athletes
who underwent ACLR implicated contralateral limb com-
pensations, including abnormal frontal-plane mechanics,
combined for a most predictive model of secondary ACL
injury risk.74 These seminal findings indicate that these
abnormal and asymmetrical biomechanical and neuromus-
cular control profiles are likely both residual to, and exacer-
bated by, the initial injury. The most efficacious
intervention strategies should target these modifiable
impairments to optimize the safe return to high-risk
activity.

Post-ACLR rehabilitation protocols have evolved greatly
over the past few decades, shifting from conservative efforts
of prolonged immobilization with delayed strengthening75 to
current paradigms that advocate immediate weightbearing,
early motion and progressive strengthening, and neuromus-
cular training. Despite these efforts, muscle weak-
ness,19,46,70,81 impaired movement,17,33,34,46,71,77 abnormal
neuromuscular control,74,88,90 and difficulty returning to
sports3,35 are common for many months after ACLR. Impor-
tantly, secondary ACL injury risk appears to be strongly
related to multiplanar movement asymmetries of the lower
extremities.74 In this Current Concepts article, we present
the latest evidence related to risk factors associated with graft
failure or secondary (contralateral) injury and our recommen-
dations for a new approach to return-to-sport training after
ACLR that is focused on resolution of neuromuscular deficits
that are known modifiable risk factors that persist following
ACLR and rehabilitation of this highest risk population.

REDUCED FUNCTION AND NEUROMUSCULAR
CONTROL AFTER ACLR

Muscle weakness, joint effusion, lack of normal joint range
of motion, and impaired function are nearly ubiquitous in
the days, weeks, and even months after ACLR. In combina-
tion, these impairments can significantly alter neuromuscu-
lar control of the reconstructed knee. Recovery of quadriceps
function, in particular, has long been advocated as a means
to optimize function in the athlete after ACLR.15,22,40,41,46,82

The persistence of knee extensor weakness is common for
several months after surgery9,11,40,51,93 and is strongly
related to the presence of abnormal movements during

activities of daily living.46,54,85 Athletes who underwent
ACLR with at least a 20% deficit in quadriceps strength
symmetry walk with truncated knee motion and a gait pat-
tern characteristic of acutely injured athletes.46 However,
normal quadriceps strength does not ensure normal neuro-
muscular movement patterns, even during simple func-
tional tasks. Six months after ACLR, athletes who
demonstrate involved limb isometric quadriceps strength
recovery (at least 90% of their uninvolved limb) continued
to walk with reduced knee motion34 and altered knee joint
moments.77 While enhancement of quadriceps strength is
a necessary component for the optimization of knee function
after an injury, restoration of normal neuromuscular control
in athletes after ACLR, which can influence the safe return
to sport, is clearly multifactorial in nature.

Reports of return-to-sport success after ACLR are
highly varied and are likely attributable, in part, to the
wide spectrum of criteria upon which ‘‘success’’ is defined.
Medical clearance, self-reported return to sport, and
achievement of minimum performance criteria to begin
sport reintegration are all common barometers of return-
to-sport success reported in the literature.3,35,44,53 How-
ever, what is consistent between studies is the absence of
ubiquitous functional success after ACLR.3,10,35 Ardern
and colleagues3 reported that within 1 year after ACLR,
two thirds of athletes had not attempted a full return to
their previous level of activity. Of the athletes who had
not returned to sport within the first postoperative year,
less than 50% indicated an intention to return to sport.

Two-year functional outcomes data from the Multicen-
ter Orthopaedic Outcomes Network (MOON) group indi-
cate that less than 50% of athletes after ACLR return to
sport.20 A steady functional decline appears common in
the years after ACLR.2,84 Therefore, resumption of the pre-
vious level of activity and continued participation in the
desired sport after ACLR are far from guaranteed from
ACLR and standardized rehabilitation.

Asymmetrical movement patterns of athletes early after
ACLR are well described17,35,46,54 and understood to per-
sist for several months, and even years, after sur-
gery.12,16,33,71,74,77 Primarily, postsurgical biomechanical
studies on athletes who underwent ACLR have been per-
formed using activities of daily living.17,34,46,77,86 Trun-
cated motions and reduced joint moments of the involved
knee have been identified during level walking up to 2
years after ACLR.33,34,77,86 More dynamic tasks that repli-
cate sport-specific movements only accentuate the

*Address correspondence to Timothy E. Hewett, PhD, The Sports Health and Performance Institute, The Ohio State University, 2050 Kenny Road, Suite
3100, Columbus, OH 43221 (e-mail: tim.hewett@osumc.edu).

yThe Sports Health and Performance Institute, The Ohio State University, Columbus, Ohio.
zDepartments of Physiology and Cell Biology, Orthopaedic Surgery, Family Medicine and Biomedical Engineering, The Ohio State University, Colum-

bus, Ohio.
§The Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio.
||Departments of Pediatrics and Orthopaedic Surgery, College of Medicine, University of Cincinnati, Ohio.
{Departments of Athletic Training, Sports Orthopaedics, and Pediatric Science, Rocky Mountain University of Health Professions, Provo, Utah.
#Athletic Training Division, School of Allied Medical Professions, The Ohio State University, Columbus, Ohio.

One or more of the authors has declared the following potential conflict of interest or source of funding: Funding support received from National Insti-
tutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH/NIAMS) grants R01-AR049735, R01-AR05563, and R01-
AR056259. The authors also acknowledge funding support from National Football League (NFL) Charities and equipment from The Ohio State University
and Cincinnati Children’s Hospital Medical Center.

Vol. 41, No. 1, 2013 Injury Prevention After ACL Reconstruction 217

movement abnormalities of these athletes after ACLR.69

The drop vertical jump landing task has exposed signifi-
cant asymmetries in multidimensional kinematics at the
hip and knee as well as force generation and attenuation
in athletes up to 4 years after ACLR.12,16,52,71,74

Abnormal movement patterns after an ACL rupture are
not isolated to the injured knee alone. There is mounting
evidence of a bilateral neuromuscular response to an ACL
injury that persists and may even be exacerbated after
reconstruction.23,33,87 Voluntary activation deficits have
been noted in both limbs after an ACL injury, despite
improvements after surgery.87 In a small group of active
athletes who underwent ACLR, changes in knee kinematics
and kinetics were noted in both limbs 3 months after sur-
gery.23 Specifically, peak knee angles, moments, and joint
powers were higher in the uninvolved limb of athletes after
ACLR when compared with controls and to their own unin-
jured limb. Interestingly, these behaviors are not unlike
those in athletes with acute ACL deficiency.6,17,78,79,86

Neuromuscular adaptations of the hip on the unin-
volved side also appear characteristic of athletes who
underwent ACLR.74,77 A longitudinal gait analysis of 26
noncopers up to 2 years after ACLR revealed contralateral
hip adaptations that manifested early after the injury and
persisted 6 months after surgery.77 These athletes demon-
strated hip power generation in the involved hip early in
weight acceptance, while the uninvolved hip absorbed
power.77 Compensatory strategies of the uninvolved hip
were the primary predictor of risk in athletes who went
on to a secondary ACL injury within 1 year of returning
to sports activity.74 As 1 of 4 predictive factors in a highly
specific and sensitive model for secondary ACL injury risk,
the transverse-plane uninvolved hip net moment impulse
early during landing independently predicted the risk of
a secondary injury with 77% sensitivity and 81% specific-
ity. These data highlight 2 major findings: (1) ACLR alone
does not fully abate the neuromuscular deficits and asym-
metries incurred as a result of injury, and (2) assessment
and treatment of bilateral limb compensations during
rehabilitation appear necessary to obtain a comprehensive
clinical picture of postoperative movement deficiencies.

RISK FACTORS FOR SECONDARY ACL INJURY

Much like primary ACL injuries, the majority of secondary
ACL injuries are caused by noncontact mechanisms,92 under-
scoring altered intrinsic neuromuscular control as an impor-
tant factor in injury risk. The risk of a secondary ACL
rupture is, at a minimum, several times greater than that
of primary ACL injury risk.73 As expected, higher levels of
postreconstruction activity are associated with a higher inci-
dence of a secondary ACL injury.81 Reports of the incidence of
graft rupture and contralateral limb injury range from 6% to
32%,4,39,46,74,80,81 and risk level may be sex specific. In a longi-
tudinal study of 180 athletes over a 15-year period, ACL graft
rupture was reported to be more likely in men.47 A prospec-
tive cohort study of over 1400 athletes after ACLR found that
while graft rupture rates did not differ between sexes, the
contralateral injury rate was higher in female than in male

athletes.81 Similarly, in a group of 63 athletes cleared to
return to sport after ACLR, 14 of the 42 (33%) female athletes
went on to a contralateral ACL rupture within 1 year.
Female athletes represented 88% of the documented contra-
lateral limb ACL injuries.73

Recent reports have indicated that neuromuscular
impairments are also predictive of a secondary ACL injury
in athletic youth.74 Fifty-six athletes after ACLR who
were medically cleared for sports participation underwent
3-dimensional biomechanical analyses and postural stabil-
ity testing and then were prospectively followed for 1 year
to document the movement characteristics predictive of sec-
ondary ACL injuries.74 Thirteen of the 56 young athletes
sustained a second ACL injury within the year. Regression
analyses indicated 4 predictive factors for secondary injury
risk with excellent specificity (88%) and sensitivity (92%):
uninvolved hip rotation net moment impulse during land-
ing, frontal-plane knee motion during landing, sagittal-
plane knee moment asymmetries at initial contact, and def-
icits in postural stability on the reconstructed limb. The
highly predictive model of second injury risk underscores
the importance of targeted return-to-sport rehabilitation,
as all predictors were modifiable in nature.

Other factors, like age and sex, also appear related to sec-
ondary ACL injury risk. Younger athletes have demonstrated
the highest reinjury rate81 and may have an increased risk of
a contralateral injury39,47 when compared with older ath-
letes. Female gender was associated with a lower postsurgi-
cal activity level20,84 and was associated with a decreased
likelihood of returning to sport within 1 year after ACLR3

when compared with their male counterparts. While these
nonmodifiable factors may significantly contribute to second-
ary injury risk and incidence, further research must investi-
gate their influence on identified modifiable factors on the
risk profile for athletes who underwent ACLR.

Impairments after ACLR can be profound; however, out-
comes after revision ACLR in athletes are reportedly worse.
Poor outcomes after ACL revision are documented by several
groups on hundreds of athletes and range from poor func-
tional abilities to an increased prevalence of degenerative
changes.5,7,20,30,84,91 However, little data document the
return-to-sport success in this population. Revision proce-
dures are associated with a lower activity level20 and lower
self-reported knee-specific outcomes scores.84 Similar to pri-
mary ACLR outcomes, return-to-sport estimates range from
60% to 93% within 4 years of revision.5,30 Second revision
rates are as high as 25% within 6 years of primary ACL revi-
sion.5 While an ACL revision may mitigate significant phys-
ical function deficits after graft failure, its effect on improving
high-level function and mental health factors may be negligi-
ble.91 In summary, revision ACLR may be viewed as a salvage
procedure,5 and robust and effective strategies to prevent the
need for such surgical intervention must be employed.

METHODS TO IDENTIFY POST-ACLR
NEUROMUSCULAR IMPAIRMENTS

The importance of early and accurate identification of post-
surgical impairments in athletes nearing medical discharge

218 Hewett et al The American Journal of Sports Medicine

has been extensively detailed. Performance on a battery of
clinically administered tests has been advocated by many
to capture and address residual impairments in strength
and function after ACLR.25,27,48,53,85 The influence of quad-
riceps strength on function after ACLR is well estab-
lished.15,22,46 Therefore, testing quadriceps strength
symmetry is an important component of the criteria for
rehabilitation progression to sports-specific tasks and even-
tually for discharge to unrestricted sports activity. While
deficits in hamstring strength were unrelated to functional
performance tasks in athletes 6 months after ACLR,41 the
ratio of hamstring-to-quadriceps torque production appears
to be a key variable in the primary ACL injury risk model.63

Strength symmetry of at least 85% is now advocated for ath-
letes beginning reintegration into cutting, pivoting, and
jumping sports.25,35,85

Dynamic single-limb task tests can capture important
deficits in function of the reconstructed knee that may be
otherwise obscured by double-limb performance tests.69

Performance on the single-limb hop test for distance on
ACL-deficient patients predicted their self-reported func-
tion 1 year after ACLR with 71% sensitivity and specific-
ity.32 A combination of agility and plyometric testing was
used to differentiate between the physical performance
characteristics of athletes who underwent ACLR and con-
trols.69 Side-to-side asymmetries in the single-limb hop
tests, not the double-limb bilateral tasks, were required
to discern between groups. In light of new evidence high-
lighting the implications of asymmetrical movement pat-
terns after ACLR, reducing limb asymmetries before
returning to sport appears imperative for maximized per-
formance and reduction of secondary ACL injury risk.74

LATE-PHASE POSTOPERATIVE REHABILITATION:
EVIDENCE FOR SPORTS PERFORMANCE
SYMMETRY TRAINING

Current postoperative rehabilitation guidelines for athletes
after ACLR advocate criterion-based progression through
knee range of motion, strengthening, and sport-specific
activities.1,67,68,89 Achievement of symmetrical joint mobil-
ity, strength, and functional performance are common crite-
ria for medical discharge to return to sport.1,35,44,68

However, there is a lack of objective criteria by which ade-
quate dynamic neuromuscular control is defined for athletes
who will return to high-velocity, high-load maneuvers.67

Neuromuscular and movement asymmetries are known to
predict primary ACL injury risk37,58,83 but have only
recently been identified as risk factors for a second ACL
injury,74 thus highlighting the potential positive effects of
a targeted neuromuscular training program that empha-
sizes movement symmetry before the return to sport.

Our proposed late postoperative rehabilitation and
sports performance symmetry training is based on the find-
ings of the prospective cohort study performed in our labora-
tory that examined neuromuscular and biomechanical
factors related to second injury risk.74 Four measures of
neuromuscular asymmetry, representing all 3 planes of
motion, were found to accurately predict second ACL injury

risk74 and are represented graphically in Figure 1. Over
a dozen therapeutic exercises have been proposed as a novel
method for primary ACL injury prevention, all based on
data from several epidemiological and interventional stud-
ies evaluating primary injury risk.** Based on the current
state of the available evidence, we surmise that these exer-
cises may adequately remediate the neuromuscular asym-
metries implicated in secondary ACL injury risk.67,74

Persistent muscle weakness of the ACL-injured limb is
known to influence postsurgical function.15,21,22,41,46 There
appears to be a preferential loss of quadriceps strength,43

but not hamstring strength,42 after an ACL injury. Expect-
edly, recovery of quadriceps strength is important in restoring
normal knee function,46 as persistent weakness of the quadri-
ceps may adversely affect sport-specific function because of
their primary role as force attenuators and generators about
the knee. While deficits in hamstring strength are character-
istic of athletes who go on to their first ACL injury,58,83 its
influence on function after ACLR is not well defined.41

The coordinated coactivation of the hamstrings and
quadriceps may play a role in mitigating primary injury
risk by way of reducing ligament strain29 and promoting
normal landing mechanics.26 Balanced agonist and antago-
nist coactivation may also protect the reconstructed knee
against second ACL injury risk via similar protective mech-
anisms. Deficits in the neuromuscular coordination of the
hamstrings and quadriceps on the reconstructed limb may
manifest as excessive landing contact noise during both
double- and single-legged landing tasks.56 Impairments
in hamstrings force steadiness, or the ability of the ham-
string muscles to produce force without variation, were
observed on isokinetic testing in athletes after ACLR with
a semitendinosus-gracilis autograft. Decreased hamstring

Hip Rotational Control Deficits Excessive Frontal Plane Knee Mechanics

Knee Flexor Deficits Postural Control Deficits

Asymmetries

Figure 1. Schematic representation of the 4 measures of
neuromuscular asymmetry highly predictive of second injury
risk in athletes who underwent anterior cruciate ligament
reconstruction.

**References 36, 38, 55, 57, 59-61, 64, 65, 72.

Vol. 41, No. 1, 2013 Injury Prevention After ACL Reconstruction 219

force steadiness was associated with poorer single-legged
hop test performance an average of 14 months after sur-
gery.8 Therefore, progressive single-limb landing activities,
like anterior and lateral jumping progressions (Figure 2),
may not only accentuate post-ACLR limb deficits69 but can
also provide an excellent training tool to help athletes avoid
quadriceps-dominant landing techniques56 and achieve the
desired level of sports performance symmetry.

Importantly, neuromuscular and biomechanical abnor-
malities and asymmetries can occur in spite of adequate
muscle strength, muscle symmetry,36,77 and sports activity
status71,74; these may be evident for years after ACLR.12,35

Based on current data detailing the increased rate of con-
tralateral injuries in female athletes,73,81 the prevalence
and persistence of asymmetrical movement strategies in
the months and years after ACLR, and the accuracy with
which limb asymmetries predict second injury risk,74 res-
toration of sports performance symmetry may aid signifi-
cantly in the reduction of second ACL injury risk.67,68

Neuromuscular training, in various forms, has been
effectively used in the prevention of ACL injuries,36,38,60

enhancing function22,24,53 and movement behaviors13,18

early after the injury, and improving function76 and move-
ment behaviors after ACLR.35 The tuck jump (Figure 3) is
a dynamic, repeated double-limb jumping task that requires
excellent trunk and lower extremity neuromuscular control
to perform properly. It not only highlights sports perfor-
mance asymmetry in all 3 planes of motion62 but may also
be effective in the treatment of movement deficits before
the return to sport.61,67 Force attenuation under high load

conditions is commonly impaired after ACLR12,71,74 and
has meaningful implications for second injury risk.74 Post-
operative and return-to-sport rehabilitation programs that
challenge dynamic neuromuscular control, facilitate tech-
nique perfection, and enhance limb symmetry may also suc-
cessfully reduce the movement impairments associated with
second injury risk; the effectiveness of these training pro-
grams has not yet been evaluated.

While high frontal-plane loading at the knee alone is
predictive of a primary ACL injury,37 it appears that a com-
bination of multiplane neuromuscular patterns is predic-
tive of secondary injury risk.74 This risk profile
highlights the influence of post-ACLR adaptations in
both limbs on secondary injury risk and underscores

Figure 2. Examples of single-leg anterior (A) and lateral (B)
progression activities. These tasks can aid the sports medi-
cine clinician both in identifying and treating clinically impor-
tant, bilateral neuromuscular dysfunction after anterior
cruciate ligament reconstruction.

Figure 3. Proper tuck jump technique. The athlete begins in
deep hip and knee flexion and swings the arms backward in
preparation for the jump. The goal is to minimize frontal-
plane motion of the trunk and lower extremities while achiev-
ing a thigh position that is parallel to the floor at the height of
the jump. The sports medicine clinician should view the ath-
lete during repeated jumps in both the sagittal and frontal
planes to identify takeoff and landing asymmetries.

Figure 4. Schematic representation of how anterior cruciate
ligament reconstruction can drive postsurgical symmetries
and neuromuscular deficits. These impairments are, in turn,
minimized with sports symmetry training and preventative
multiplane dynamic movement tasks.

220 Hewett et al The American Journal of Sports Medicine

evidence indicating the importance of sports performance
symmetry before returning to unrestricted activity. Our
proposed treatment paradigm (Figure 4) focuses on resto-
ration of symmetrical function during the critically impor-
tant period when common rehabilitation programs end but
many neuromuscular deficits often persist.

RETURN TO SPORT AFTER ACLR: OBJECTIVE
ASSESSMENT VERSUS TIME AFTER SURGERY

Historically, return-to-sport clearance was based on time;
sports medicine professionals often allowed the return to
sport 6 months after surgery.4,44 In light of emerging evi-
dence that indicates athletes are at increased risk for a sec-
ond injury within the first 7 months after ACLR,45 we
advocate serial function and strength testing throughout
the late rehabilitation phase to identify the neuromuscular
strategies that may further increase this risk.57,74

Current investigations indicated that young athletes
assessed after medical release and return to sport demon-
strate measurable functional deficits after ACLR that are
independent of the time from surgery.66 These data further
support the current approaches to target functional deficits
related to a second injury before reintegration back to sport.
In young female athletes, decreased hamstring strength
was associated with an increased risk of an ACL injury, while
young female athletes with similar hamstring-to-quadriceps
ratios to that of male athletes had a reduced risk to go onto
an ACL injury.58 The cumulative data indicate that reduced
hamstring strength and recruitment is related to initial and
likely secondary injury risk, which supports the use of isoki-
netic testing in return-to-sport decision making and guidance
of interventions to reduce the risk of a second injury.

Prior studies emphasize the need to utilize objective
tools that are sensitive to limb-to-limb deficits and to
develop rehabilitation protocols that are targeted to elimi-
nate limb asymmetries.66,67,69,71,74 Use of functional
assessments, as opposed to temporally guided or graft-
specific decision making, can support a safer return to
sport for competitive athletes.68

CONCLUSION

To optimize functional and clinical outcomes after ACLR and
to prevent a second knee injury, an EBM approach is pro-
posed in this review that directly addresses known, modifi-
able neuromuscular and biomechanical risk factors for
increased risk of second ACL tears.84 Optimal return to sport
after ACLR appears to be predicated on numerous postsurgi-
cal factors.74,92 Second ACL injury risk is most strongly
related to modifiable postsurgical factors74 and is specific to
the magnitude of multiplanar limb asymmetries. Inadequate
neuromuscular control and biomechanical asymmetries of the
trunk and lower extremities predict first knee injury risk.37,94

Addressing these impairments in athletes after ACLR using
targeted rehabilitation may significantly reduce the second
injury incidence and subsequent functional disability. The
proposed EBM approach will target these highly impactful

impairments by way of focused sports symmetry training to
optimize the safe return to high-risk activity and increase
both the efficiency and efficacy of intervention strategies.

ACKNOWLEDGMENT

The authors acknowledge the expert data collection
machines and The Sports Medicine Biodynamics Center
research teams at The Ohio State University and Cincin-
nati Children’s Hospital Medical Center.

An online CME course associated with this article is
available for 1 AMA PRA Category 1 CreditTM at http://
ajsm-cme.sagepub.com. In accordance with the standards
of the Accreditation Council for Continuing Medical Edu-
cation (ACCME), it is the policy of The American Ortho-
paedic Society for Sports Medicine that authors, editors,
and planners disclose to the learners all financial rela-
tionships during the past 12 months with any commercial
interest (A ‘commercial interest’ is any entity producing,
marketing, re-selling, or distributing health care goods
or services consumed by, or used on, patients). Any and
all disclosures are provided in the online journal CME
area which is provided to all participants before they
actually take the CME activity. In accordance with
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K N E E

Psychological predictors of anterior cruciate ligamen

t

reconstruction outcomes: a systematic review

Joshua S. Everhart • Thomas M. Best •

David C. Flaniga

n

Received: 5 April 2013 / Accepted: 27 September 2013 / Published online: 15 October 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose Lack of return to sport following anterior cru

–

ciate ligament (ACL) reconstruction often occurs despit

e

adequate restoration of knee function, and there is growin

g

evidence that psychological difference among patients ma

y

play an important role in this discrepancy. The purpose o

f

this review is to identify baseline psychological factors that

are predictive of clinically relevant ACL reconstruction

outcomes, including return to sport, rehab compliance

,

knee pain, and knee

function.

Methods A systematic search was performed in PubMed,

Google Scholar, CINAHL, UptoDate, Cochrane Reviews,

and SportDiscus, which identified 1,633 studies fo

r

potential inclusion. Inclusion criteria included (1) pro-

spective design, (2) participants underwent ACL recon-

struction, (3) psychological traits assessed at baseline, an

d

(4) outcome measures such as return to sport, rehabilitation

compliance, and knee symptoms assessed. Methodological

quality was evaluated with a modified Coleman score wi

th

several item-specific revisions to improve relevance

to

injury risk assessment studies in sports medicine.

Results Eight prospective studies were included (modi-

fied Coleman score 63 ± 4.9/90, range 55–72). Average

study size was 83 ± 42 patients with median 9-month

follow-up (range 3–60 months). Measures of self-efficacy,

self-motivation, and optimism were predictive of rehabili-

tation compliance, return to sport, and self-rated knee

symptoms. Pre-operative stress was negatively predictive,

and measures of social support were positively predictive

of knee symptoms and rehabilitation compliance. Kine-

siophobia and pain catastrophizing at the first rehabilitation

appointment did not predict knee symptoms throughout the

early rehabilitation phase (n.s.

).

Conclusions Patient psychological factors are predictive

of ACL reconstruction outcomes. Self-confidence, opti-

mism, and self-motivation are predictive of outcomes,

which is consistent with the theory of self-efficacy. Stress,

social support, and athletic self-identity are predictive of

outcomes, which is consistent with the global relationsh

i

p

between stress, health, and the

buffering hypothesis of

social support.

Level of evidence Systematic review of prospective

prognostic studies, Level II.

Keywords Sports � Knee surgery � Psychology �
Sports medicine outcomes � Risk assessment

Introduction

Sports-related knee surgery is a common procedure in the

USA, with approximately 130,000 anterior cruciate liga-

ment (ACL) reconstructions and 500,000 meniscus-related

procedures performed annually [30]. In the elective knee

surgery setting, an essential component of the initial

evaluation is an assessment of potential benefit and risk of

J. S. Everhart � D. C. Flanigan (&

)

Department of Orthopaedics, The Ohio State University Wexner

Medical Center, Suite 3100 Morehouse Medical Plaza 2050

Kenny Road, Columbus, OH 43221, USA

e-mail: david.flanigan@osumc.edu

T. M. Be

st

Department of Family Medicine, The Ohio State University

Wexner Medical Center, Columbus,

OH, USA

T. M. Best � D. C. Flanigan
OSU Sports Medicine, Sports Health and Performance Institute,

The Ohio State University Wexner Medical Center, Columbus,

OH, USA

123

Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762

DOI 10.1007/s00167-013-2699-1

surgery versus the time and cost burden of operative

treatment and knee rehabilitation. Selection of an appro-

priate treatment strategy requires a thorough assessment of

patient lifestyle and treatment expectations, along with

consideration of factors such as pre-injury activity level,

desire to return to sport, occupational demands, willingnes

s

to complete postoperative rehabilitation, and expectations

regarding postoperative knee function [16].

Despite this, variable sports-related outcomes continue

to be reported in selected patient populations [3, 4, 16].

Even after primary ACL reconstruction in an athleti

c

population with high rates of rehabilitation compliance,

a

disappointing rate of return to previous level of sport par-

ticipation ranging between 47 and 70 % is reported at

greater than 4-year follow-up [3–5, 16, 39]. In many cases,

this lack of return to sport occurs without significant

functional deficits in knee stability and strength and with-

out persistent pain [3, 4, 16, 34, 39, 41]. Another factor to

consider is that return to sport after ACLR may not be

in

the patient’s best interest if he or she is primarily interested

in avoiding additional injury, as primary ACLR patients are

at increased risk of injury to both the ipsilateral and con-

tralateral limb [9, 59].

Psychological differences between patients may be an

important contributing factor to this apparent mismatch

between postoperative knee function scores (successful

physiological outcomes) and rates of return to sport or pre-

injury activity levels (successful participation-related out-

comes) [4, 5]. Differences in psychological and behav-

ioural responses to pain are some of the most well-studied

factors that may contribute to a lack of return to sport [2, 4,

5]. Due to the trauma of acute injury, discomfort during

knee rehabilitation, and residual knee symptoms, some

patients may fall into a pattern of behaviours similar to

what is observed in patients with chronic pain syndromes

[2, 10, 31].

Three basic psychological theories are tested in the

studies included in this review. We have presented these

theoretical frameworks in the context of ACL injury,

reconstruction, and rehabilitation in a series of conceptual

diagrams (Fig. 1). The fear-avoidance model of pain is a

cognitive-behavioural theory originally developed by Le-

them et al. [37]; this model has persisted for several dec-

ades and has been extensively validated [35]. In this model,

when patients experience a recurrent painful stimulus, an

exaggerated negative psychological response to pain or the

anticipation of pain (pain catastrophizing) [50] leads to an

active avoidance of movement out of fear of recurrent pain

or injury (kinesiophobia) [51]. The theory of self-

efficacy

was originally proposed by Bandura [6]. In this theory,

individuals have intrinsic levels of self-efficacy, optimism,

and self-motivation, which are considered to be stab

le

personality traits (unchanging from year to year) and are

strongly associated with higher rates of task completion in

rehabilitation [1, 48] and exercise adherence [18]. Finally,

stress, health, and the buffering hypothesis of social sup-

port were developed by Cohen [12, 13]. In this model,

psychological stress is believed to globally affect physical

and mental health [63], and an individual’s degree of social

support is believed to modulate this effect [13, 57]. One’s

perceived level of social support can be derived from a

variety of relationships; of particular importance in spor

ts

medicine are athletic self-identity and the team environ-

ment as a source of social support [24, 62], which can be

negatively impacted by injury [62].

Ardern et al. [4] recently demonstrate a consistent

association between psychological factors and returning to

sport after ACL injury. However, their review focuses on

cross-sectional analyses, and they comment that prognostic

studies are necessary to facilitate inferences regarding

causation. The purpose of this systematic review is to

address this gap in knowledge by identifying psychological

traits that have been demonstrated in a prospective manner

to increase risk of an unsatisfactory outcome after ACL

reconstruction. Specifically, this review is designed to

identify baseline psychological traits in patients

Fig. 1 Conceptual diagrams of the fear-avoidance model of pain (a),
the theory of self-efficacy (b), and stress, health, and the buffering
hypothesis of social support (c) in the context of ACL reconstruction

Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762 753

123

undergoing ACL reconstruction that are predictive of

clinically relevant outcomes, including return to sport, knee

rehabilitation compliance, and postoperative knee pain and

function.

Materials and methods

Initial search and primary screening

The guidelines outlined in the PRISMA statement for

standardized reporting of systematic reviews were adhered

to in the preparation of this manuscript [38]. A search was

performed on the PubMed database (1975 to June, 2012)

with the Medical Subject Headings (MeSH) advanced

search tool (Fig. 2). Systematic searches were also per-

formed in CINAHL, UptoDate, Google Scholar, Cochrane

Reviews, and SportDiscus in addition to hand searching of

reference lists of key publications. The titles and abstracts

of the studies identified in the initial screen were then

individually reviewed for the following selection criteria:

1. Studies investigating ACL reconstruction outcomes.

2. Study population consists primarily of physically

active individuals of any experience level with a mean

age 13–65 years.

3. Prospective study design.

4. Predictive assessment of psychological factors as an

injury risk factor was either a primary or seconda

ry

aim of the study.

5. Study is reported in manuscript form in a peer-

reviewed publication. Meeting abstracts, posters, and

thesis papers were excluded.

6. Study reports original research in English.

Nineteen studies met inclusion criteria. The design and

methodology of which were reviewed to determine whe-

ther their analysis and findings were directly applicable to

the objective of this review. Eight studies were excluded

because of their focus on cross-sectional comparisons

between psychological factors and outcome measures [10,

19, 32, 36, 44–46, 56]. Two prospective studies were

rejected because they included psychological testing as pa

rt

of their outcome measures but not their baseline measures

[28, 40]. Finally, one prospective study was excluded

because it consisted of a mixed surgical and non-surgical

population [26], resulting in a final total of nine studies

included in this review.

Assessment and risk of bias

In order to assess the quality of the nine selected studies,

the study authors used a modified Coleman score; the

original Coleman score was utilized as an orthopaedic

quality assessment tool for patellar tendinopathy outcomes

studies [14]. Modifications of several items in part A of the

original Coleman score were made in either content or

language to improve their relevance to injury risk assess-

ment studies in sports medicine. Item 3 was changed fro

m

‘‘number of different surgical procedures’’ to ‘‘number of

different screening tests’’ included in each reported out-

come. Item 6 was changed from ‘‘description of surgical

procedure’’ to ‘‘description of clinical screening test’’. Item

7 of the original Coleman score was removed, the content

of which originally pertained to sufficient description of the

study rehabilitation protocol.

Theoretical frameworks and grouping of psychological

scales

As is the case in sports medicine, there are often multiple

clinical scales available to behavioural psychologists to

measure the same general factor; therefore, to facilitate

interpretation, we have grouped the individual scales used

by the included studies according to the psychological

theory being tested (Table 1).

Data collection and reporting

The surgical procedure, patient demographics, sample size,

length of follow-up, pre-operative measures, and outcome

measures for all included studies were systematically iden-

tified and recorded (Table 2). The description of study

Fig. 2 Study flowchart

754 Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762

123

findings was limited to pre-operative psychological facto

rs

and their predictive assessment of knee-related outcomes.

Effect sizes of the identified psychological risk factors were

reported as available from the study manuscript. We did not

perform any secondary calculations with the reported data

with the exception of Gobbi et al.’s [23] descriptive data for

the psychovitality scale; in this case, the authors used an

appropriate nonparametric test (Mann–Whitney U) but

reported inappropriate descriptive statistics (means instead

of medians with interquartile ranges) for these non-normally

distributed data. Finally, though the psychological scales

presented in this paper apply to one of three theories (Fig. 2),

there are insufficient validation studies in the current litera-

ture between scales in a given category to provide a mean-

ingful pooled estimate or perform a meta-analysis.

Results

Study characteristics

A total of eight prospective cohort studies were included

for review based on our screening methodology and

inclusion criteria (Table 2). All studies included both sexes

and did not differentiate between levels of sports compe-

tition in their analyses. Mean ages ranged from 22 to

32 years [11, 52]. Sample size ranged from 38 to 100

(mean 71 ± 22 patients) [23, 54] and duration of follow-up

ranged from 3 to 60 months [11, 52].

Quality assessment with modified Coleman score

None of the studies fulfilled all of the criteria in the modified

Coleman score (Table 3). The mean modified Coleman

score 63 ± 5 out of 90, with a range of 55–72. The studies

achieved a mean score of 41 ± 3 out of 50 points on part A,

which primarily evaluates baseline study characteristics. The

studies scored worse on part B (mean 22 ± 3 points out of

40), which primarily evaluates outcome criteria and

recruitment rates. Of the individual factors on the modified

Coleman score, item 2 had the lowest number of studies that

met the specified criteria (2/8 studies), which required a

mean follow-up of at least 2 years.

Fear-avoidance model of pain

There were negative findings regarding the psychological

response to pain or fear of re-injury and knee surgery

Table 1 Study scale definitions

Underlying theory Category Acronym Scale name Factor assessed

Fear-avoidance model of pain

[37

]

Fear-avoidance response

to

injury

PCS [50] Pain Catastrophizing

Scale

Emotional response to pain

TSK-11 [61] Tampa Scale for

Kinesiophobia

Fear of activity and re-injury

Theory of self-efficacy [6] Optimism and self-

efficacy

SIS[29] Sports Injury Survey Self-reported use of positive coping

skills during rehabilitation

SSP [25] Swedish universities

Scales of Personality

Survey of personality traits

including optimism & pessimism

(embittermen

t)

SER [58] Modified Self-Efficacy for

Rehabilitation Outcome

Scale

Perceived ability to perform tasks

during injury rehabilitation

K-SES[53] Knee Self-Efficacy Scale Perceived ability to perform knee-

related tasks

Self-motivation ACL-RSI [60] ACL-Return to Sport after

Injury scale

Perceived ability and motivation to

return to sport

SMI [21] Self-motivation inventory Self-motivation to complete a task

Psychovitality

[23]

Psychovitality Scale Motivation and perceived

likelihood to return to sport after

injury

Stress, health, and the

buffering hypothesis of

social support [13]

Stress and social

support

in the context of athletic

injury

BSI [17] Brief Symptom Inventory Psychological distress

ERAIQ [49] Emotional Responses of

Athletes to Injury

Questionnaire

Emotional impact of injury and

perceived social support

SSI Social support inventory Overall perceived social support

AIMS Athletic Identity

Measurement scale

Athletic self-identity (a source of

social support among athletes)

Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762 755

123

T
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),
c
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e
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&

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,
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n

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P

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it
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(K
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a
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h
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m
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,

1
le

g
h

o
p

d
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ta
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c
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(h
o
p

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d

e
x

sc

o
re

),

a

c
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v
it

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(T

e
g

n
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r

a
c
ti

v
it

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sc

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re
)

A
ft

e
r
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i

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f

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a
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,

se
lf

–

m

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v
a
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(S
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w

a
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(r
=

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p
\

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5
)

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c
o
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p
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(r
=

0
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p
\
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0
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),
so

c
ia
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p
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(S

S
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w
a
s

a
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o
c
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d
w
it

h
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m
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c
o
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p
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ti
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(r
=
0
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2
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p
\
0
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5
),

a
th
le
ti

c
id

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w
a
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a
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o
c
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d
w
it

h
k

n
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la
x
it
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(r
=

0
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8
,
p
\
0
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),
h

o
p

in
d

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x
sc
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(r

=
0

.2
6
,

p
\
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),
a
n
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(L
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sh
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m
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)
(r
=
0
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7
,

p
\
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a
n

d
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re
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(B
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w
a
s
a
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o
c
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d
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it
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(r
=

–
0

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5
2

,

p
\
0
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)

6
3

B
re

w
e
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t
a
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[7
]

P
re

-o
p

e
ra
ti
v
e
b
a
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li
n
e
a
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d
6
-m
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fo
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=

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1

,
2

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m
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,
4

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g
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(S
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it
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(a
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,

&
c
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)

A
g

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tc
o

m
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T
h

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w
a
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in
to

th
re

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a
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ro

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(

m
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1

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,
m
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2
4

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m

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3

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a
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o
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A
s

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b
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(d

e
p

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t

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a
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)

a
n

d
1

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a
th
le
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c
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ti
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b

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c
a
m

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m
o
re

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(s
ta

n
d

a
rd

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e
d

c
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n
t

b

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=
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se

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6
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756 Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762

123

T
a
b
le

2
c
o

n
ti

n
u

e
d
A
u

th
o

r
T
im
in
g
o
f
a
ss
e
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m
e
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tu
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p
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a
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a
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e

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u

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o
m

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m
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a
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S
tu
d
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re
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M
o
d
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e
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C
o
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m
a
n
sc
o
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P

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c
h

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a
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in
T
a
b

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2

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h
m

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w
sk

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t
a
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[1
1

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P
o

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b
a
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(1

st

re
h
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b
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tm

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a
n
d
3
-m
o

n
th

fo
ll
o
w
-u
p
a
ss
e
ss
m
e
n
ts
N
=

7
7

,
4

1
m

a
le

,
3

6
fe

m
a
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,
m
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a
n
a
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7

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7
in
ju

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d
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g
sp
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K
n

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m
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n

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rn

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ti
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a
l
k
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c
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m
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n
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te

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b

je
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IK
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,

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n

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m

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ri

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ra

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sc
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fo
r

p

a
in

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R

S
),

k
in

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si

o
p
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b
ia

(T
S

K
-1

1
),

p
a
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c
a
ta

st
ro

p
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in
g

(P
C

S
),
se
lf

-e
ffi

c
a
c
y

(S
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R
)

K
n
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m
p
to
m
s

(N
R

S
,

IK
D

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)

K
in

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si

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b

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(T
S
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-1

1
)

a
n
d

se
lf
–
e
ffi
c
a
c
y
(S
E
R
)

a
t

th
e

fi
rs

t
re
h
a
b
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it
a
ti
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a
p
p

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in

tm
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t

(b
a
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e
)

d
id

n
o

t
p

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d

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t

1
2

w
e

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k

p
o

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o

p
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ra
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a
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(N
R

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)

o
r
k
n
e
e

fu
n

c
ti
o
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sc
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re
s

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K

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a
ft

e
r
a
d
ju
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fo

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,

se
x

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a
n

d
b

a
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li
n
e
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in
(N
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w
it
h
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ra

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h

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l
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re
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)

5
5

G
o

b
b

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a
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d

F
ra

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is

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o

[2
3
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P
re
-o
p
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ra
ti
v
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b
a
se
li
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e
a
n
d
1
2
-m
o
n
th
fo
ll
o
w
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e
ss
m
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N
=

1
0

0
,

6
7

m
a
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,
3

3
fe

m
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m
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n
a
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8
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rs
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a
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1
7

–
5

0
),

b
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c
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m

p
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ti
v
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a
n
d
re
c
re
a
ti
o
n
a
l
a
th
le
te
s
K
n
e
e
sy
m
p
to
m
s
(I
K

D
C

a
n
d

S
A

N
E

),
a
c
ti

v
it
y
le

v

e
ls

(T
e

g
n

e
r

a
n
d

M
a
rx

a
c
ti
v
it
y
sc
a
le

s)
,

a
n
d
m
o
ti
v
a
ti
o
n

to
re

tu
rn

to
sp

o
rt

(p
sy

c
h

o
v

it
a
li

ty
)

K
n
e
e

is
o

k
in
e
ti

c
st

re
n

g
th

,
k
n
e
e
m
o
ti
o

n
a
n

a
ly

si
s,

r

e
tu

rn
to

sp
o

rt

P
sy

c
h
o
v
it
a
li

ty
sc

o
re

s
si

g
n

ifi

c
a
n

tl
y

d
if

fe
re

d
b
e
tw
e
e
n

p
a
ti

e
n

t

s
w

h
o

re
tu

rn
e
d

to
sp
o
rt

(n
=

2
4
p
a
ti
e
n

ts
)

a
t
1
2

m
o
n

th
s

(m
e
d

ia
n

1
6

p
o

in
ts

IQ
R

1
4

–
1

8

)
a
n
d
n
o
n
–
re
tu

rn
e
rs

(n
=
2
4
p
a
ti
e
n
ts
)
(m
e
d
ia
n

9
p

o
in

ts
IQ

R
8

–
1
5
)

(p
\

0
.0
0
1

,
M

a
n

n
–

W
h

it
n

e
y

U
)

7
2

L
a
n

g
fo

rd
e
t

a
l.

[3
3
]

P

o
st

o
p
e
ra

ti
v
e
b
a
se
li
n

e
(a

t

3
-m

o
n

th
)

a
n
d
1
2
-m
o
n
th
fo
ll
o
w
-u
p
a
ss
e
ss
m
e
n
ts
N
=

8
7

,
5

5
m

a
le
,
3

2
fe

m
a
le
,
m
e
a
n
a
g
e
2

7
.5

±
5

.7
y

e
a
rs

,

a
ll

p
a
rt
ic
ip
a
n
ts

p
la

y
e
d

sp
o

rt
s

o
n

w
e
e
k

ly
b

a
si

s
p

ri
o

r
to

in
ju
ry

D
is

tr
e
ss

d
u

e
to

a
th
le
ti

c
in

ju
ry

(

E
R

A
IQ

),
m

o
ti
v
a
ti
o
n
to
re
tu
rn
to
sp
o

rt
(A

C
L

-R
S

I)
K
n
e
e
is
o
k
in
e
ti
c
st
re
n
g
th

,
la

x
it

y
,

L
a
c
h

m
a
n

/p
iv

o
t

sh
if

t
te

st
,

ra
n

g
e
o
f
m
o
ti
o

n
,

p
re

se
n

c
e
o
f
e
ff

u
si

o
n
,

si
n

g
le

h
o

p
/c

ro
ss

-o
v

e
r
h
o
p

p
e
rf

o
rm
a
n
c
e
A
C

L
-R

S
I

a
t

6
m

o
n
th
s
w
a
s

si
g

n
ifi

c
a
n
tl
y

h
ig

h
e
r

in
a
th

le
te
s

w
h

o
re
tu
rn
e
d
to
sp
o
rt
a
t
1
2
m
o
n
th
s

(m
e
a
n

6
3

.

2
±

1
7

.2
)

th
a
n

n
o

n
-r

e
tu
rn
e
rs
(m
e
a
n

5
1

.

8
±

1
6

.8
)

(

p
=

0
.0

0
5

).
A

tr
e
n
d

to
w

a
rd
s
si

g
n
ifi

c
a
n
c
e

w
a
s
o
b

se
rv

e
d
fo
r
d
if
fe
re

n
c
e
s

in
E
R
A
IQ

sc
o
re

s
b
e
tw

e
e
n
re
tu
rn
e
rs
a
n
d
n
o
n

-r
e
tu

rn
e
rs
a
ft
e
r
a
d
ju
st
m
e
n
t
fo

r
a
ss

e
ss
m
e
n

t
ti

m
e
p
o

in
t

(p
=
0
.0
8
,

tw
o

-f
a
c
to

r

re
p
e

a
te

d
-m

e
a
su
re
s

A
N

O
V

A
).

E
R
A
IQ
sc
o
re

s
d
id

n
o
t

si
g
n
ifi
c
a
n
tl
y
d
if

fe
r

b
e
tw
e
e
n
re
tu
rn
e
rs
a
n
d
n
o
n
-r
e
tu
rn
e
rs
(p
=
0
.0

8
);

n
o
a
d
ju
st
m
e
n

t
w

a
s

n
e
c
e
ss

a
ry

fo
r

a
g
e
,

g
ra

ft
-t

im
e
,

ti
m

e
b

e
tw
e
e
n
in
ju

ry
a
n

d
su

rg
e
ry

,
o
r
a
c
ti
v
it
y
le

v
e
ls

a
s
a
ll

w
e
re

n
o

n
–

si
g
n
ifi
c
a
n

t
c
o
v

a
ri
a
te

s
(p

[
0

.0
5

)
6
3

Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762 757

123

T
a
b
le
2
c
o
n
ti
n
u
e
d
A
u
th
o
r
T
im
in
g
o
f
a
ss
e
ss
m
e
n
ts
S
tu
d
y
p
a
rt
ic
ip
a
n
ts
B
a
se
li
n
e
m
e
a
su
re
s
O
u
tc
o
m
e
m
e
a
su
re
s
S
tu
d
y
re
su
lt
s
M
o
d
ifi
e
d
C
o
le
m
a
n
sc
o
re
P
sy
c
h
o
lo
g
ic
a
l
sc
a
le
s
d
e
fi
n
e
d
in
T
a
b
le
2

S
c
h

e
rz

e
r
e
t
a
l.

[4
7

]
P
o
st
o
p
e
ra
ti
v
e
b
a
se
li
n
e
(1
st
re
h
a
b
il
it
a
ti
o
n
a
p
p
o
in
tm
e
n
t)
a
n

d
6

m
o
n
th
fo
ll
o
w
-u
p
a
ss
e
ss
m
e
n
ts
N
=

5
4

,
1

7
fe

m
a
le
,
3

7
m

a
le
,
m
e
a
n
a
g
e
2
8
±
8
y
e
a
rs
5
2
%
c
o
m
p
e
ti
ti
v
e
a
n
d

4
6

%
re
c
re
a
ti
o
n
a
l
a
th
le
te
s
P
o
si
ti
v
e
c
o

p
in

g
sk

il
ls

d
u
ri
n
g
re
h
a
b
il
it
a
ti
o
n

(S
IS

)
R
e
h
a
b
il
it
a
ti
o
n
e
ff
o
rt
(S
IR
A
S
)
a
n
d
c
o
m
p
li
a
n
c
e
(a
tt
e
n
d
a
n
c
e
,
h
o
m
e
e
x
e
rc
is
e
a
n
d
c
ry
o
th
e
ra
p
y
c
o
m
p
le
ti
o
n
)
A
ft
e
r
a
d
ju
st
m
e
n
t
fo

r
c
o

v
a
ri

a
te
s
w
it
h
m

u
lt

ip
le

re
g
re
ss
io
n
a
n
a
ly
si
s,

u
se

o
f
g
o
a
l

se
tt

in
g
a
s
a
p
o
si
ti
v
e
c
o
p
in

g
st

ra
te

g
y

w
a
s
p
re

d
ic

ti
v

e
o

f
h
o
m
e
e
x
e
rc
is
e
c
o
m
p
le
ti
o
n
(b
e
ta
=
0

.3
5

,
p
\

0
.0
5
)
in
a
d

d
it

io
n
to
re
h
a
b
il
it
a
ti
o
n
e
ff
o
rt
(S
IR
A
S

)
(b

e
ta
=
0

.5
1

,
p
\
0
.0
0
5

).
U

se
o

f
p

o
si
ti
v

e
se

lf
–

ta
lk

a
s

a
c
o

p
in
g
st
ra
te
g
y
w
a
s

c
o
rr

e
la
te
d
w
it

h
h
o
m

e
e
x
e
rc

is
e
c
o
m
p
le
ti
o
n
(r
=

0
.5

2
,
p
\
0
.0
5
)

in
u

n
a
d

ju
st
e
d
c
o

rr
e
la

ti
o
n
a
n
a
ly

si
s

6
4

S
w

ir
tu

n
a
n
d

R
e
n

st
rö

m

[5
2
]

P
re
-o
p
e
ra
ti
v
e
b
a
se
li
n
e
a
n
d
6
0
-m
o
n
th
fo
ll
o
w
-u
p
a
ss
e
ss
m
e
n
ts
N
=
5
7
a
t
b
a
se
li
n
e
,
4
6
a
t
fo
ll
o
w
-u
p
,
m
e
a
n
a
g
e
3
2
±

7
.9

y
e
a
rs

.
2

2
/4

6
p
a
ti
e
n

ts
u

n
d

e
rw

e
n

t
A

L
C

R
(a

v
e
ra

g
e

9
m

o
n
th
s
a
ft
e
r

d
a
te

o
f
in
ju

ry
),

2
4

/4
6

p
a
ti
e
n

ts
h

a
d
A
C

L
R

,
2

4
/4

6
n
o

n
-o

p
e
ra
ti
v
e
m

a
n
a
g

e
m
e
n
t

P
e
rs

o
n
a
li

ty
tr

a
it

s
(S

S
P

)
a
n
d

a
c
ti
v
it
y

le
v

e
ls
(T
e
g

n
e
r)

K
n
e
e
sy
m
p
to
m
s

(k
n

e
e
in
ju
ry
a
n
d
o
st
e
o
a
rt

h
ri

ti
s

o
u
tc
o
m
e
sc
o

re
–

K
O

O
S

)
a
n

d
a
c
ti

v
it
y
le
v
e
ls
(T
e
g
n
e
r)

L
o

w
p

e
ss

im
is

m
sc
o
re
s
w
e
re
a
ss
o
c
ia
te
d
w
it
h
h

ig
h

e
r
K
O
O
S
sc
o
re
s

(S
p

e
a
rm

a
n

’s
rh

o
=

–
0
.3
6
,
p
\
0
.0

5
).

N
o

a
d
ju
st
m
e
n
t
fo
r
a
g
e
o
r
p
re

-i
n
ju

ry
a
c
ti

v
it
y
le
v
e
ls
w
a
s
p
e
rf
o
rm
e
d
a
s
b
o
th
m
e
a
su
re
s

h
a
d

n
o

n
-s

ig
n

ifi
c
a
n

t
c
o
rr
e
la

ti
o
n
s

w
it

h
o

u
tc

o
m
e
s
(p
[
0
.0
5
)
6
7
T
h
o
m

e
é

[5
5
]

P
re
-o
p
b
a
se
li
n
e
,
1
2
-m
o
n
th
fo
ll
o
w
-u
p
N
=

3
8

,
1
3
fe
m
a
le
,
2
5
m
a
le
,
m
e
a
n
a
g
e
2

9
.7

y
e
a
rs
(r
a
n
g
e
1
6
–
5
5
)

A
c
ti

v
it
y
le
v
e
ls
(T
e
g
n
e
r)

,
a
n
d

se
lf
–
e
ffi
c
a
c
y

(K
-S

E
S

)
A
c
ti
v
it
y
le
v
e
ls
(T
e
g
n
e
r
a
n
d

p
h
y
si

c
a
l
a
c
ti
v
it
y
sc
a
le

-P
A

S
)

k
n
e
e

sy
m
p
to
m
s

(K
O

O
S
a
n

d
L

y
sh

o
lm

k
n
e
e
sy
m
p
to
m
sc
o
re

),
a
n
d

o
n
e

le
g

h
o

p
(h

o
p
in
d
e
x
sc
o

re
)

P
e
rc

e
iv

e
d
se
lf
-e
ffi
c
a
c
y
a
t
c
o
m
p
le
ti
n
g
k
n

e
e
-r

e
la
te
d

ta
sk

s
in

th
e

f

u
tu

re
(K

-S
E

S
-f

u
tu
re
)
w
a
s
p
re
d
ic
ti
v
e
o
f
a
n

a
c
c
e
p
ta

b
le
o
u
tc
o
m
e

a
c
c
o
rd

in
g

to
K

O
O

S
sc
o
re

(s
p
o
rt

s-
re

c
re
a
ti
o
n

O
R

1
.6

,
p
=
0
.0

0
2

;
q

u
a
li

ty
o

f
li

fe
O

R
1

.5
,

p
=
0
.0

3
7

),
T

e
g
n
e
r
sc
o

re
(O

R

1
.7

,
p
=
0

.0
0
3

),
o

r
h

o
p

in
d
e
x

sc
o
re
(O

R
2

.2
,

p
=
0
.0

4
).

P
a
ti

e
n
ts

w
e
re

c
la

ss
ifi

e
d
a
s

h
a
v
in

g
a
n

‘‘
a
c
c
e
p

ta
b

le
o

u
tc
o
m

e
’’

if
th

e
y
h
a
d

a
p
o
st

o
p
e
ra
ti
v
e

d
e
c
re

a
se
in

T
e
g
n
e
r

a
c
ti
v
it
y
sc
o
re

(c
o
m

p
a
re

d

to
p

re
-i

n
ju

ry
le

v
e
ls

)
o

f
B

2
,
a
p
o
st
o
p
e
ra
ti
v

e
K

O
O

S
-s

p
o

rt
s/

re
c
re
a
ti
o
n
o
r
K
O
O
S

-q
u
a
li

ty
o
f

li
fe

su
b
sc
o

re
o

f
[

7
6

o
r

a
h

o
p
in
d
e
x
sc
o
re
o
f
[

9
0

%

5
9

758 Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762

123

outcomes in the included studies (Table 2). In particular,

Chmielewski et al. [11] reported no association between

kinesiophobia (TSK-11) and pain catastrophizing (PCS) at

the first rehabilitation appointment and knee symptoms at

12 weeks postsurgery after adjustment for age, sex, and

baseline knee pain (NRS) with hierarchical regression

modelling (n.s.); however, interpretations of this negative

finding are limited by the study timeframe, which only

includes the early postoperative rehabilitation phase.

Theory of self-efficacy

A significant relationship was demonstrated between fac-

tors that contribute to a patient’s general belief or confi-

dence in a successful recovery and the actual outcome from

surgery (Table 2). Thomeé et al. [54] found that perceived

self-efficacy at completing knee-related tasks in the future

(K-SES-future) was predictive of an acceptable outcome

according to KOOS score, Tegner activity score, or hop

index score. Similar associations were reported by Gobbi

et al. [23] and Langford et al. [33] between measures of

perceived ability and benefit of returning to sport (psych-

ovitality and ACL-RSI scores, respectively) and actual

return to sport at 12-month follow-up. Finally,

Swirtun and

Renström [52] found that patients with low pessimism

scores (high optimism) had higher KOOS scores at 5-year

follow-up (Spearman’s rho = -0.36, p \ 0.05).
Self-efficacy in general was also found to affect reha-

bilitation-specific outcome measures (Table 2). Scherzer

et al. [47] found that patients who utilized goal setting or

positive self-talk had had greater rates of home exercise

completion and higher perceived effort during rehabilita-

tion. Brewer et al. [8] found that patients with higher self-

motivation (SMI) were more compliant with home exercise

programs (r = 0.48, p \ 0.001) and had greater effort
during rehabilitation (SIRAS) (r = 0.26, p \ 0.05). A

follow-up cohort study by the same research group [7]

found that the strength of this relationship appears to be age

dependent, with self-motivation being a stronger predictor

of home exercise completion in older patients

(beta = 0.25, p \ 0.05).

Stress, health, and the buffering hypothesis of social

support

There was some evidence to support an association

between stress, social support, and knee surgery outcomes

(Table 2). Specifically, Langford et al. [33] found a trend

towards significance for differences in ERAIQ scores

among athletes who returned to sport at 12 months and

non-returners after adjustment for assessment time point

(p = 0.08, two-factor repeated-measures ANOVA).

Brewer et al. [8] found that higher levels of stress (BSI)

were associated with increased knee laxity, and athletic

identity (AIMS) was associated with decreased knee laxity;

social support (SSI) was positively associated with home

exercise completion (r = 0.22, p \ 0.05). Brewer et al. [7]
demonstrated that as age increases, the relationship

between athletic identity and knee outcomes becomes less

significant, and social support becomes more significant.

Discussion

The most important finding of this systematic review is that

several psychological factors have been consistently dem-

onstrated to be predictive of postoperative outcomes fol-

lowing ACL reconstruction. Sports-related knee surgery

requires a substantial rehabilitative effort on the part of the

patient to achieve a satisfactory outcome. Additionally,

patients must be ready and willing to overcome the fear of

re-injury to return to their original level of activity and

Table 3 Modified Coleman scores

Study Part A Part B Total

score
1 2 3 4 5 6 Total 7 8 9 Total

Brewer et al. [8] 10 0 7 15 5 5 42 12 4 5 21 63

Brewer et al. [7] 10 0 7 15 5 5 42 12 6 0 18 60

Chmielewski et al. [11] 10 0 0 15 5 5 35 12 8 0 20 55

Gobbi and Francisco

[23]

10 5 7 15 5 3 45 4 11 12 27 72

Langford et al. [33] 10 0 7 15 5 3 40 0 8 15 23 63

Scherzer et al. [47] 10 0 0 15 5 5 39 7 8 10 25 64

Swirtun and

Renström [52]

7 0 7 15 5 5 44 12 8 5 23 67

Thomeé et al. [54] 7 5 7 15 5 5 39 7 11 5 20 59

Average score 40 ± 3.6 22 ± 2.9 63 ± 4.9

Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762 759

123

sports participation. This relationship between patient

psychological traits and postoperative outcomes may par-

tially explain why a subset of patients fail to return to sport

despite adequate surgical restoration of knee function.

There is a consistent relationship between patients’ self-

confidence, optimism, and motivation to recover from

injury and the actual outcome of knee surgery [8, 23, 52,

54]. These factors likely contribute to a patient’s psycho-

logical ‘‘readiness’’ for knee surgery and the subsequent

rehabilitation process. This concept is supported by Ban-

dura’s theory of self-efficacy, which describes the rela-

tionship between intrinsic levels of perceived self-efficacy

(confidence in the ability to complete a task) and actual

behaviour (follow-through) [6]. The majority of studies in

this review lend support to our proposed theoretical

framework of self-efficacy in the context of ACL injury,

surgery, and rehabilitation (Fig. 2), as their measures self-

motivation, self-efficacy, and optimism were associated

with future knee pain, function, and return to sport [7, 8,

23, 33, 47, 54]. Because global measures related to self-

efficacy such as intrinsic optimism [52] and intrinsic self-

motivation [8] are considered to be stable (unchanging

within a year) personality traits, a pre-operative assessment

of these factors to gauge a patient’s psychological ‘‘readi-

ness’’ for sports-related knee surgery has the potential to

help guide individualized treatment recommendations.

The relationship between stress, social support (either

general or in relation to athletic identity), and knee surgery

outcomes is not surprising, as these factors also have an

effect on compliance with medical treatment, overall

quality of life, and general health status [20, 22, 43]. In

particular, levels of stress and perceived social support

appear to affect objective outcomes such as rates of return

to sport in addition to subjective outcomes such as self-

reported pain severity [33, 46]. An interesting age-specific

relationship in which pre-operative activity levels more

positively affect knee surgery outcomes in younger athletes

was identified by several studies in this review. The posi-

tive association between activity levels and outcomes may

be partially due to increased athletic self-identity, which

Brewer et al. [7] postulate is a source of positive social

support in younger individuals (\30 years age). Younger
athletes may derive greater perceived social support from

sports participation than older adults; conversely, surgery

outcomes for older adults (30–40 years) were less strongly

associated with athletic self-identity and more strongly

associated with a general social support index SSI [7].

Investigators should be cognizant of the potential modify-

ing effect of age on these factors when interpreting sports-

related surgical outcomes in a population containing mul-

tiple age groups. Additionally, clinicians and physical

therapists should be aware that younger patients in partic-

ular may be negatively affected by loss of sports

participation and a team environment as a source of social

support. An appropriate way to counterbalance this loss of

social support would be to encourage use of positive cop-

ing strategies such as positive self-talk and goal setting as

described by Scherzer et al. [47] Finally, though stress is

responsive to treatment, routine screening of patients

without any prior indication of either condition may lead to

a high rate of false positives and an unnecessary number of

referrals to mental health professionals. Therefore, addi-

tional research is needed to determine the strength of

relationship between stress and surgical outcomes to more

appropriately assess the risk versus benefit of mental health

screening in a sports medicine setting.

The fear-avoidance model has an important role in

patient behaviour following knee surgery, as kinesiophobia

(negative response towards pain) and pain catastrophizing

(active avoidance of activities out of fear of recurrent pain

and injury) are two psychological factors that are strongly

correlated with lack of return to sport [2, 4, 32, 34, 56].

However, the current review is unable to characterize the

ability of pre-operative screening of patients for heightened

pain catastrophizing and kinesiophobia to predict levels of

these factors after knee rehabilitation. Likely, the negative

findings reported by Chmielewski et al. [11] are largely due

to an inadequate follow-up period, as the range of activities

allowed at 12 weeks postsurgery is far different from full

clearance of sports activities after rehabilitation comple-

tion. Further research with adequate follow-up is indicated

to determine the prognostic role, if any, that a baseline

assessment of pain perceptions or fear of recurrent injury

has on knee surgery outcomes.

The limitations of this review are primarily related to the

quality and design of the included studies. Our review

included prospective studies only, and the quality of studies

included in our review as assessed by the modified Cole-

man score (mean 62.9/90) is comparable to other recent

systematic reviews on sports medicine topics by Mithoefer

et al. [42] (mean 58/100), Cowan et al. [15] (mean 59/100)

and Harris et al. [27] (mean 54/100). However, the major

limitation of our review is that the relationship between

psychological factors and knee surgery outcomes is likely

understated. Two common shortcomings of the included

studies were a small sample size and short follow-up per-

iod, both of which lead to a decreased ability to detect

clinically significant relationships between baseline psy-

chological factors and knee surgery outcomes. Negative

findings were reported for a primary or secondary study

aim in at least 3 of 8 studies, but only one study reported a

power analysis or reasons why a sample size could not be

estimated a priori [11, 33, 52]. Additionally, inadequate

follow-up may minimize the observed effect of psycho-

logical factors on outcomes due to incomplete improve-

ment in knee symptoms and function in many patients at

760 Knee Surg Sports Traumatol Arthrosc (2015) 23:752–762

123

that time point. Finally, use of differing outcome measures

(return to sport, symptom scales, physiological measures,

and measures of compliance) and ceiling effects of symp-

tom scales can both increase false negative error rates.

Conclusion

In conclusion, patient psychological factors are predictive

of ACL reconstruction outcomes. Self-confidence, opti-
mism, and self-motivation are predictive of outcomes,

which is consistent with the theory of self-efficacy.

Stress, social support, and athletic self-identity are pre-

dictive of outcomes, which is consistent with the global

relationship between stress, health, and the buffering

hypothesis of social support. Additional research is nee-

ded to determine the potential role of psychological

screening as a pre-operative predictive tool for knee

surgery outcomes or alternatively as an opportunity for

risk factor intervention.

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• Psychological predictors of anterior cruciate ligament reconstruction outcomes: a systematic review

Abstract
Purpose
Methods
Results
Conclusions
Level of evidence
Introduction
Materials and methods
Initial search and primary screening
Assessment and risk of bias
Theoretical frameworks and grouping of psychological scales
Data collection and reporting
Results
Study characteristics
Quality assessment with modified Coleman score
Fear-avoidance model of pain
Theory of self-efficacy
Stress, health, and the buffering hypothesis of social support
Discussion
Conclusion
References

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