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Int J Sports Phys Ther
Int J Sports Phys Ther
2159
International Journal of Sports Physical Therapy
2159-2896
NASMI Website: International Journal of Sports Physical Therapy

34386294
25463
10.26603/001c.25463
Clinical Commentary/Current Concept Review
ACL Return to Sport Testing: It’s Time to Step up Our Game
Unverzagt Casey PT, DPT, DSc, OCS, SCS, FAAOMPT 1
Andreyo Evan PT, DPT, OCS, SCS 2
Tompkins Jeff PT, DPT, OCS 3
1 Physical Therapy, Robbins College of Health and Human Sciences Baylor University https://ror.org/005781934
2 Health Sciences Rocky Mountain University of Health Professions https://ror.org/02egdz393
3 Wise Physical Therapy and Sports Medicine
Corresponding author: Casey Unverzagt Department of Physical Therapy, Robbins College of Health and Human Sciences, Baylor University, One Bear Place #97193, Waco, TX 76798. Telephone 972 576 9069. Fax 254 710 3870. casey_unverzagt@baylor.edu
1 8 2021
2021
16 4 11691177
27 11 2020
9 4 2021
© The Author(s)
https://creativecommons.org/licenses/by-nc-sa/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike License (4.0) which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited. If you remix, transform, or build upon this work, you must distribute your contributions under the same license as the original.

Patients and physicians have long looked to physical therapists to help determine an athlete’s readiness to return to sport (RTS) following anterior cruciate ligament reconstruction (ACLR). This is a complex decision that must take into account biological healing, joint stability, functional performance, and psychological readiness. Considering that the vast majority of medical professionals use time as the sole determinant of an athlete’s readiness, and few are using performance-based criteria, it appears as though our profession is failing to capture the necessary information to make this weighty recommendation. The time is now to take a hard look at current practice patterns with RTS testing and push the envelope forward. The purpose of this clinical commentary is challenge our failing status quo by disseminating a robust model for RTS testing that incorporates temporal and criterion-based factors, as well as intrinsic and extrinsic data.

Level of Evidence

5

knee
movement system
return to sport testing
hop testing
return to sport
acl
==== Body
pmcReviewing Current Practice Patterns

Anterior cruciate ligament (ACL) injuries are all too common in athletic participation. Sources have reported the incidence as high as 200,000 ACL injuries per year in the United States alone.1 It is customary in the United States to pursue anterior cruciate ligament reconstruction (ACLR) after injury in order to return to the previous level of sport. While many healthcare professionals and athletes are painfully aware of how common ACL injuries are, few realize, or at least openly acknowledge, that the likelihood of returning to sport is far from guaranteed. Pooled data from a systematic review and meta-analysis found that only 65% of individuals returned to their preinjury level of sports participation following an ACLR, with only 55% going on to participate in competitive sports.2 Other studies have shown that, of those athletes under 25 years of age, approximately 23-29% will go on to incur a second ACL injury.3,4 While there are many factors to consider when reviewing this data, it should, at minimum, cause us all to question whether the current state of ACL management is acceptable. Stakeholders would benefit from taking a step back and reflecting on whether current practice patterns reflect what is truly in an athlete’s best interest.

Sports medicine personnel should acknowledge and respond to the problem of high reinjury rates and relatively low rates of returning to sport. A recent scoping review identified the most common criteria used to clear individuals to RTS after primary ACLR.5 Of the 209 studies reviewed, 85% reported the use of time as a criterion for RTS, with 42% using it as the sole criterion.5 This fixation on using time as a RTS determinant is deeply engrained in the physical therapy profession, so much so that ever since Dr. Shelbourne began discussing accelerated rehabilitation after ACLR in the 1990’s, patients and sports medicine providers have pushed the speed limits of rehab. Kevin Wilk spoke to this in 2005,6(p51) poignantly noting, “Speeding through the rehabilitation program may have more risks than benefits. When we speed in our automobiles we may be caught by the law and pay a fine. If we speed in the rehabilitation program, we may have to suffer more significant consequences—patients with unsatisfactory knee function for the rest of their lives.” The authors of this manuscript argue that the majority of sports medicine professionals – physicians and physical therapists alike – are dangerously exceeding the speed limits of rehab.

Looking closer at the issue of time as a RTS determinant, Burgi et al.5 noted that 72% of practitioners use ≥6 to <9 months as their standard to clear an athlete for play. Is waiting six to nine months sufficient to maximize potential for a safe RTS? The vast majority of the time, the answer is an emphatic, NO! Cristiani et al.7 found that of 4093 individuals assessed at six-months post-operative ACLR, only 35% and 47% achieved ≥90% limb symmetry for isokinetic quadriceps and hamstring strength, respectively. Additionally, only 67% achieved ≥90% limb symmetry for a single-leg hop test. Collectively, only 19.6% achieved symmetrical knee function with all three standardized tests (isokinetic quadriceps strength, isokinetic hamstring strength, and single-leg hop test). Similar data has been shown for athletes nine months post-operatively, noting that only 11% of subjects (7 of 62) passed RTS testing that included the Landing Error Scoring System, three single-leg hop tasks, isokinetic quadriceps and hamstring strength, as well as two outcome measures (IKDC and ACL-RSI).8 A similar study had equally striking findings, noting a seven-fold greater risk of injury for individuals who RTS before nine months post-operatively.9

Some authors have gone so far to suggest that RTS should be delayed until two years after ACLR,3 noting that baseline joint health and function are not typically achieved until 24 months post-operatively; thus, delaying RTS until this is achieved significantly reduces the incidence of second ACL tears.3 While this may scream in the face of current practice patterns, the sports medicine community should not be quick to discount it.

The use of a limb symmetry index (LSI) is of particular interest when qualifying someone’s RTS readiness.  It is vital to appreciate that symmetry may not correlate with movement quality nor does it indicate whether the athlete has achieved pre-injury status or acceptable population norms. Gokeler et al.10(p948) notes, “An athlete may have perfect limb symmetry and yet be underprepared to compete because both extremities are much weaker or more poorly controlled than a healthy athlete.” Despite these shortcomings, LSI is often used in association with strength and hop testing. While there is considerable variation between studies regarding an acceptable LSI, the majority of authors suggest that a LSI of 85-90% is satisfactory.5 While this may be normative practice, is it truly best practice? Gokeler et al.10(p949-950) goes on to note that, “Despite achieving a LSI > 90%, patients demonstrated significant and clinical relevant deficits in performance for both limbs when compared to normative data from healthy athletes.” A similar study, albeit small, demonstrated that individuals achieving a LSI of >93% still exhibited markedly asymmetrical movement patterns during hop testing.11 A larger study revealed that athletes who achieved >90% LSI for strength and hop testing did not achieve 90% of their estimated pre-injury capacity with the same tests.12 At best, all of these athletes likely demonstrate compensatory adaptations (eg. detraining) on their uninvolved extremity; at worst, they demonstrate involuntary neurologic inhibition of the uninvolved limb due to the contralateral ACL tear.

No matter the mechanism, one can conclude that using LSI for hop testing and strength assessment has the potential to overestimate knee function. Therefore, interpretation of this data must be done cautiously.10 To be clear, the authors of this manuscript are not suggesting practitioners abandon LSI altogether; instead, the authors advocate for careful interpretation of the data in addition to raising the bar for what is considered passing. Clinical practice guidelines recommend a minimum of 90% LSI, yet advocate for a much higher standard of up to 100% symmetry.13 It is the opinion of the authors that despite the limitations associated with using LSI for RTS testing, and the apparent lack of consensus regarding passing scores, athletes should aim for 100% LSI for both strength and hop testing, with 97% the lower cutoff for hop testing and 90% the lower cutoff for isokinetic strength testing.

Another area that should draw attention in current practice is the use of patient-reported criteria. For example, in Burgi’s scoping review,5 only 12% of studies assessed personal or contextual factors, including confidence and self-reported knee function. The low utilization of patient-reported assessments contrasts recommendations from recent literature demonstrating that lower psychological readiness correlates with a higher risk of second ACL injury when returning to play among younger patients.14 Lower psychological readiness can also lessen the likelihood that an individual returns to sport at all, inciting fear of reinjury and decreased self-efficacy, even after one is deemed physically ready to return to play.15

As readers evaluate current practice patterns for ACL injury management, it is important to compare how these stand up to current recommendations. A consensus statement on RTS from the First Congress in Sports Physical Therapy outlines five specific recommendations to guide the practitioner when deciding to clear an individual for RTS.16

Use a group of tests (aka: a test battery).

Choose open tasks (less controlled) over closed tasks (more controlled) when possible.

Include tests with reactive decision-making elements.

Assess psychological readiness to RTS.

Monitor workload throughout the RTS transition.

When examining these recommendations in light of current practice patterns,5 it is clear that a sizeable gap exists. In retrospect, it appears as though the sports medicine community may have a monocular, often short-sighted view of ACL rehabilitation and RTS testing, which may be a notable contributor to low RTS rates as well as high reinjury rates. In response to this hypothesis, the authors of this manuscript aim to disseminate a robust model for RTS testing that incorporates temporal and criterion-based factors, as well as intrinsic and extrinsic data.

Let’s Get Back to the Basics

It is commonplace for sports physical therapists to commence an athlete’s rehabilitation by creating a needs analysis that details his or her athletic demands. Take for instance, a high school soccer player. The athlete needs to be able to sprint, cut, jump, hop, take contact from other players, give contact to other players, rapidly accelerate, and rapidly decelerate, all while filtering the onslaught of visual, proprioceptive, vestibular and somatosensory inputs. In short, the athletic demands of soccer (or any sport at that), are complex and not easily captured by one or two simple tests. Therefore, using the individualized needs analysis, specific targeted interventions and functional testing can be developed in preparation for the athlete to RTS.

While every sport is unique and criteria must be tailored for individual needs, many commonalities span athletes of all levels, positions, and sports. Table 1 offers the reader a list of extrinsic criteria that most athletes will require to minimize the potential for re-injury, along with the various means of measuring the variable. While the proposed list is not exhaustive, it offers a practical testing battery when completing RTS testing based on available literature. Table 2 provides the rationale for the proposed recommended cut-off values.8,10,12,15,17–32

64699 Table 1. Extrinsic Criterion Used to Assess Return to Sport Readiness*

Extrinsic Criterion	Means of Measuring	
Range of motion	Hip, knee & ankle (tibial shaft angle)	
Neuromuscular control	Functional Movement Screen, Y-Balance Test,
Single leg squat, Tuck Jump Assessment,
Landing Error Scoring System	
Strength	Isokinetic testing: time to peak torque, peak torque	
Power	Hop testing:
Anterior hop, triple hop, triple crossover hop, timed hop, hop & stop	
Agility and cutting	Trazer lateral agility screen, Trazer Flanker test, reactive agility test	
Psychologic readiness	ACL-Return to Sport After Injury, 2000 IKDC Questionnaire**	
*Means of measuring should be left to the discretion of the evaluating facility.<br>**IKDC: International Knee Documentation Committee

The vast majority of applied research to date has focused on modifiable risk-factors as criteria for RTS testing. There is an equally important arm of this discussion that needs to be explored: that of intrinsic risk factors. It is the opinion of the authors that many healthcare professionals often undervalue the influence of intrinsic risk factors on ACL reinjury when making RTS decisions. Female athletes, for example, are two to eight times more likely to sustain an ACL injury.33 Multiple anatomic factors, unable to be ameliorated by the patient, may predispose one to ACL injury.34 A list of these intrinsic risk factors is available in Table 3.34–36 While these factors may indeed be non-modifiable, their correlation with ACL tears should be acknowledged and influence one’s timeline for sports participation.

Practically speaking, the reader should compare two athletes who pass RTS testing seven-months following ACLR. Consider one patient who has no intrinsic risk factors: the athlete is male, a senior in college, and sustained a contact-related ACL tear during intramural flag football. In contrast, a 16-year-old female is also looking to go back to sport seven-months following ACLR. She has a history of a contralateral ACL tear, a family history of ACL tears, marked laxity of the knee, as well as a primary injury that was non-contact. Even if both athletes pass their respective RTS tests, the clinician should appreciate how uniquely different each athlete is, and how they should be managed as such. The authors offer specific recommendations for reconciling common intrinsic factors by delaying an athlete’s RTS and requiring them to complete a standardized ACL injury prevention program (IPP) that has been demonstrated to decrease the risk of ACL injury37,38 (Appendix 1).

Specific Testing Consideration

In order to account for the plethora of modifiable and non-modifiable risk factors associated with an ACL tear, the authors propose the use of a RTS testing battery similar to Appendix 1. Make note of the “Ticket to Entry.” These tests were selected as part of a screening tool in order to ensure the athlete is safe to undergo and complete RTS testing. If the athlete does not successfully pass the “Ticket to Entry,” they should not complete the remainder of the assessment.

64702 Figure 1. Isokinetic testing following ACLR

Given the complexity of some of the tests, as well as the necessary equipment (Figures 1-3), not all outpatient physical therapy facilities are poised to conduct RTS testing. Athletes may need to be sent to specific RTS testing centers that have the equipment and expertise in order make the determination. Finally, given the implicit bias that many physical therapists have towards their own patients, and the reality that physical therapists are not only assessing the athlete during testing but, in essence, their own performance as therapists, the authors recommend having a practitioner complete the testing who was not otherwise directly involved in the patient’s care.

64700 Table 2. Extrinsic Cut-Off Values Used to Assess Return to Sport Readiness*

Extrinsic Criterion	Source for Cuff-Off Value	
Hip, knee & ankle ROM	While the authors of the manuscript are unaware of knee ROM loss leading to a secondary ACL tear, research suggests that a loss of knee ROM is correlated with early knee osteoarthritis.17 Several studies have examined the link between a lack of closed chain dorsiflexion and increased ground reaction forces, altered knee kinematics, and increased risk of lower extremity injury18–20	
Functional Movement Screen (FMS)	The authors use a subscription-based injury prediction algorithm titled Move2Perform in order to interpret Functional Movement Screen scores. In the absence of this, a cut score of <14 with no side-to-side discrepancies has been proposed.21	
Y-Balance Test (YBT)	The authors use a subscription-based injury prediction algorithm titled Move2Perform in order to interpret Y-Balance Test scores. In the absence of this, a cut score of ≤4cm difference anteriorly and ≤6cm posterolateral and posteromedial can be used.22	
Single Leg Squat Test (SLST)	The Single Leg Squat Test has been shown to be a simple, useful test when identifying neuromuscular risk factors for an ACL tear.23	
Tuck Jump Assessment (TJA)	While a cut score of  ≤5 was originally proposed, this was based off of unpublished research.24 The authors propose elevating the standard of this test to ≤3 errors when used as part of RTS testing.	
Landing Error Scoring System	Based off Welling et al.8 and Padua et al.25	
Isokinetic testing	Based off Welling et al.8 and Tourville et al.26	
Hop testing (anterior hop, triple hop, crossover hop, timed hop)	Based off original hop test27 and more current revelations regarding limitations of hop testing and LSI10–12	
Hop & Stop Test	Based off Juris et al28	
Lateral Agility Screen	Using a Trazer movement analysis system, lateral agility is used to assess reaction time, acceleration, and deceleration speeds of the involved and uninvolved extremities. ≥95% LSI was chosen based off unpublished research and to remain fairly consistent with other cuff-off scores.	
Flanker Test	Using a Trazer movement analysis system, the Flanker test29 was used to assess reaction time, acceleration, and deceleration speeds of the involved and uninvolved extremities. ≥95% LSI was chosen based off unpublished research and to remain consistent with other cuff-off scores.	
Reactive Agility Test	Laser timing is used to assess the speed an athlete can change direction on both the involved and uninvolved lower extremity. Additionally, a scoring rubric is used to assess lower quarter biomechanics during the full-speed cutting maneuver.	
ACL Return to Sport After Injury (ACL-RSI)	Based on O’Connor et al.30 and Meierbachtol et al.15	
2000 IKDC Evaluation	Based on Cheecharern31 and Sadeqi et al.32	
*Means of measuring should be left to the discretion of the evaluating facility

64701 Table 3. Intrinsic Risk Factors Associated with ACL Re-Injury

Intrinsic Criterion	Criterion	
Gender33	Female	
Anterior knee laxity33	>3mm translation	
Mechanism of injury33	Non-contact injury	
Family history of ACL tear34	Immediate family member with history of ACL tear	
Sport participation35	Returning to Level I sport (includes jumping, hard pivoting, cutting)	
Tibial slope angle33	Steeper posterior-inferior-directed tibial plateau slope compared to uninjured athletes, as determined by surgeon	
Intercondylar femoral notch size33	Decreased notch width index compared to uninjured athletes, as determined by surgeon	
Previous ACL tear34	History of either ipsilateral and/or contralateral ACL tear	

64703 Figure 2. Reactive agility testing using laser timing gates

64704 Figure 3. Lateral agility screen using Trazer computer system

Lastly, while a thorough discussion on acute:chronic workload ratios is beyond the scope of this paper, the authors of the manuscript would be remiss to not mention the importance of the concept, especially in light of the current RTS Consensus Statement.16 Simply put, as an athlete transitions back to participation, sport, and performance, it is important to achieve and maintain optimal loading. Monitoring an athlete’s current training load (acute) against the load imposed over the preceding four weeks (chronic) provides what is known as the acute:chronic workload ratio.16 Great debate exists on and off the field regarding the utility of the acute:chronic workload ratio and its ability to predict injury. The authors refer readers to a recent systematic review detailing many of the advantages of workload monitoring, along with many of the associated controversies.39

An Uphill Battle

Utilizing temporal and criterion-based assessments when making RTS decisions, as well as considering intrinsic and extrinsic risk factors, goes against the grain. It is likely that many physicians, physical therapists, and patients may look unfavorably upon these recommendations. Additionally, the proposed RTS criteria have not yet been validated. While this approach to RTS testing may provide more information than current RTS criteria, it may also be less feasible for some clinicians and patients, considering the additional equipment, training, and time required to execute it. However, the pressures for an athlete to RTS the season following their injury should not permit clinicians to put on blinders and throw clinical reasoning out the window. Instead of focusing on getting an athlete back on the field as soon as possible, what if physical therapists were to actively shift the sports medicine culture to focus on long-term athlete health and wellness, as well as athletic viability and performance? What if therapists start seeing post-operative protocols as guides and not rules, cease conveniently simplifying RTS testing to one-dimensional methods that check a box, and instead embrace a holistic approach to evaluating an athlete’s readiness for sport? What if sports medicine providers are transparent enough to arm patients with accurate RTS and retear rates instead of pretending that waiting six to nine months to RTS guarantees success? The authors of this manuscript encourage each clinician to honestly reflect on their current practice patterns for RTS testing. The time is now to push the envelope forward. Please consider joining the movement.

Conflicts of Interest

The authors affirm that we have no financial affiliation (including research funding) or involvement with any commercial organization that has a direct financial interest in any matter included in this manuscript.

Supplementary Material

Appendix 1
==== Refs
Mechanism of injury and risk factors for anterior cruciate ligament injury Oper Tech Sports Med Wetters Nathan Weber Alexander E. Wuerz Thomas H. Schub David L. Mandelbaum Bert R. 2016
24 1 2–6 1557-9794 10.1053/j.otsm.2015.09.001
Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors Br J Sports Med Ardern Clare L Taylor Nicholas F Feller Julian A Webster Kate E 11 2014
48 21 1543 1552 0306-3674 10.1136/bjsports-2013-093398
Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport Am J Sports Med Paterno Mark V. Rauh Mitchell J. Schmitt Laura C. Ford Kevin R. Hewett Timothy E. 7 2014
42 7 1567 1573 0363-5465 10.1177/0363546514530088 24753238
Risk of secondary injury in younger athletes after anterior cruciate ligament reconstruction: a systematic review and meta-analysis Am J Sports Med Wiggins Amelia J. Grandhi Ravi K. Schneider Daniel K. Stanfield Denver Webster Kate E. Myer Gregory D. 7 2016
44 7 1861 1876 0363-5465 10.1177/0363546515621554 26772611
Which criteria are used to clear patients to return to sport after primary ACL reconstruction? a scoping review Br J Sports Med Burgi Ciara R Peters Scott Ardern Clare L Magill John R Gomez Christina D Sylvain Jonathan Reiman Michael P 2 2 2019
53 1154 1161 0306-3674 10.1136/bjsports-2018-099982
Are there speed limits in rehabilitation? J Orthop Sports Phys Ther Wilk Kevin E 2005
35 2 50–51 0190-6011 10.2519/jospt.2005.0102 PMID: 15773562 15773562
Only one patient out of five achieves symmetrical knee function 6 months after primary anterior cruciate ligament reconstruction Knee Surg Sports Traumatol Arthrosc Cristiani Riccardo Mikkelsen Christina Forssblad Magnus Engström Björn Stålman Anders 11 2019
27 11 3461 3470 0942-2056 10.1007/s00167-019-05396-4
Low rates of patients meeting return to sport criteria 9 months after anterior cruciate ligament reconstruction: a prospective longitudinal study Knee Surg Sports Traumatol Arthrosc Welling Wouter Benjaminse Anne Seil Romain Lemmink Koen Zaffagnini Stefano Gokeler Alli 12 2018
26 12 3636 3644 0942-2056 10.1007/s00167-018-4916-4
Young athletes who return to sport before 9 months after anterior cruciate ligament reconstruction have a rate of new injury 7 times that of those who delay return J Orthop Sports Phys Ther Beischer Susanne Gustavsson Linnéa Senorski Eric Hamrin Karlsson Jón Thomeé Christoffer Samuelsson Kristian Thomeé Roland 2 2020
50 2 83 90 0190-6011 10.2519/jospt.2020.9071
A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: a case control study Orthop Traumatol Surg Res Gokeler A. Welling W. Benjaminse A. Lemmink K. Seil R. Zaffagnini S. 10 2017
103 6 947 951 1877-0568 10.1016/j.otsr.2017.02.015
Adaptations in single-leg hop biomechanics following anterior cruciate ligament reconstruction Knee Surg Sports Traumatol Arthrosc Orishimo Karl F. Kremenic Ian J. Mullaney Michael J. McHugh Malachy P. Nicholas Stephen J. 11 2010
18 11 1587 1593 0942-2056 10.1007/s00167-010-1185-2
Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury J Orthop Sports Phys Ther Wellsandt Elizabeth Failla Mathew J. Snyder-Mackler Lynn 5 2017
47 5 334 338 0190-6011 10.2519/jospt.2017.7285 28355978
Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus Br J Sports Med van Melick Nicky van Cingel Robert E H Brooijmans Frans Neeter Camille van Tienen Tony Hullegie Wim Nijhuis-van der Sanden Maria W G 12 2016
50 24 1506 1515 0306-3674 10.1136/bjsports-2015-095898
Psychological readiness to return to sport is associated with second anterior cruciate ligament injuries Am J Sports Med McPherson April L. Feller Julian A. Hewett Timothy E. Webster Kate E. 3 2019
47 4 857 862 0363-5465 10.1177/0363546518825258 30753794
Psychological and functional readiness for sport following advanced group training in patients with anterior cruciate ligament reconstruction J Orthop Sports Phys Ther Meierbachtol Adam Yungtum William Paur Eric Bottoms John Chmielewski Terese L. 11 2018
48 11 864 872 0190-6011 10.2519/jospt.2018.8041
2016 consensus statement on return to sport from the First World Congress in sports physical therapy, Bern Br J Sports Med Ardern Clare L. Glasgow Philip Schneiders Anthony Witvrouw Erik Clarsen Benjamin Cools Ann Gojanovic Boris Griffin Steffan Khan Karim M. Moksnes avard H\a Mutch Stephen A. Phillips Nicola Reurink Gustaaf Sadler Robin Silbernagel Karin Grävare Thorborg Kristian Wangensteen Arnlaug Wilk Kevin E. Bizzini Mario 2016
50 14 853–864 1473-0480 10.1136/bjsports-2016-096278 PMID: 27226389 27226389
Osteoarthritis after anterior cruciate ligament reconstruction: the importance of regaining and maintaining full range of motion Sports Health Multidiscip Approach Shelbourne K. Donald Freeman Heather Gray Tinker 1 2012
4 1 79 85 1941-7381 10.1177/1941738111430201
Ankle-dorsiflexion range of motion and landing biomechanics J Athl Train Fong Chun-Man Blackburn J. Troy Norcross Marc F. McGrath Melanie Padua Darin A. 1 1 2011
46 1 5 10 1062-6050 10.4085/1062-6050-46.1.5
Weight-bearing dorsiflexion range of motion and landing biomechanics in individuals with chronic ankle instability J Athl Train Hoch Matthew C. Farwell Kelley E. Gaven Stacey L. Weinhandl Joshua T. 1 8 2015
50 8 833 839 1062-6050 10.4085/1062-6050-50.5.07
Return to play in athletes following ankle injuries Sports Health Clanton Thomas O. Matheny Lauren M. Jarvis Hannah C. Jeronimus Anastasia B. 2012
4 6 471–474 1941-7381 10.1177/1941738112463347 PMID: 24179584 24179584
Functional movement screening: the use of fundamental movements as an assessment of function - part 1 Int J Sports Phys Ther Cook Gray Burton Lee Hoogenboom Barbara J Voight Michael 2014
9 3 369 409
Star excursion balance test as a predictor of lower extremity injury in high school basketball players Res Rep Plisky Phillip J Rauh Mitchell J Kaminski Thomas W Underwood Frank B 2006
36 12 9
Neuromuscular evaluation with single-leg squat test at 6 months after anterior cruciate ligament reconstruction Orthop J Sports Med Hall Michael P. Paik Ronald S. Ware Anthony J. Mohr Karen J. Limpisvasti Orr 3 2015
3 3 232596711557590 2325-9671 10.1177/2325967115575900
Tuck jump assessment for reducing anterior cruciate ligament injury risk Athl Ther Today Myer Gregory D. Ford Kevin R. Hewett Timothy E. Hubbard Tricia J. 9 2008
13 5 39 44 1078-7895 10.1123/att.13.5.39 19936042
The landing error scoring system as a screening tool for an anterior cruciate ligament injury–prevention program in elite-youth soccer athletes J Athl Train Padua Darin A. DiStefano Lindsay J. Beutler Anthony I. de la Motte Sarah J. DiStefano Michael J. Marshall Steven W. 2 6 2015
50 6 589 595 1062-6050 10.4085/1062-6050-50.1.10
Relationship between isokinetic strength and tibiofemoral joint space width changes after anterior cruciate ligament reconstruction Am J Sports Med Tourville Timothy W. Jarrell Kathleen M. Naud Shelly Slauterbeck James R. Johnson Robert J. Beynnon Bruce D. 2 2014
42 2 302 311 0363-5465 10.1177/0363546513510672
Hop testing provides a reliable valid outcome measure during rehab after ACLR Phys Ther Reid Andrea Birmingham Trevor 2007
87 3 337–349 1464-5076 10.3109/02699206.2011.561398 PMID: 21453042 17311886
A dynamic test of lower extremity function following anterior cruciate ligament reconstruction and rehabilitation J Orthop Sports Phys Ther Juris Paul M. Phillips Edward M. Dalpe Chantell Edwards Christina Gotlin Robert S. Kane Daniel J. 10 1997
26 4 184 191 0190-6011 10.2519/jospt.1997.26.4.184
Detection of persisting concussion effects on neuromechanical responsiveness Med Sci Sports Exerc Wilkerson Gary B. Nabhan Dustin C. Prusmack Chad J. Moreau William J. 9 2018
50 9 1750 1756 0195-9131 10.1249/MSS.0000000000001647 29683918
No relationship between strength and power scores and anterior cruciate ligament return to sport after injury scale 9 months after anterior cruciate ligament reconstruction Am J Sports Med O’Connor Richard F. King Enda Richter Chris Webster Kate E. Falvey Éanna Cian 1 2020
48 1 78 84 0363-5465 10.1177/0363546519887952
Return to sport and knee functional scores after anterior cruciate ligament reconstruction: 2 to 10 years' follow-up Asia-Pac J Sports Med Arthrosc Rehabil Technol Cheecharern Sukrom 4 2018
12 22 29 2214-6873 10.1016/j.asmart.2018.01.003 29963374
Progression of the psychological ACL-RSI score and return to sport after anterior cruciate ligament reconstruction: a prospective 2-year follow-up study from the French prospective anterior cruciate ligament reconstruction cohort study (FAST) Orthop J Sports Med Sadeqi Mansour Klouche Shahnaz Bohu Yoann Herman Serge Lefevre Nicolas Gerometta Antoine 12 2018
6 12 232596711881281 2325-9671 10.1177/2325967118812819
The female ACL: Why is it more prone to injury? J Orthop 6 2016
13 2 A1 A4 0972-978X 10.1016/S0972-978X(16)00023-4
Risk factors for anterior cruciate ligament injury: a review of the literature — part 1: neuromuscular and anatomic risk Sports Health Multidiscip Approach Smith Helen C. Vacek Pamela Johnson Robert J. Slauterbeck James R. Hashemi Javad Shultz Sandra Beynnon Bruce D. 1 2012
4 1 69 78 1941-7381 10.1177/1941738111428281
Risk factors for anterior cruciate ligament injury: a review of the literature—part 2: hormonal, genetic, cognitive function, previous injury, and extrinsic risk factors Sports Health Multidiscip Approach Smith Helen C. Vacek Pamela Johnson Robert J. Slauterbeck James R. Hashemi Javad Shultz Sandra Beynnon Bruce D. 3 2012
4 2 155 161 1941-7381 10.1177/1941738111428282
Return to level I sports after anterior cruciate ligament reconstruction: evaluation of age, sex, and readiness to return criteria Orthop J Sports Med Webster Kate E. Feller Julian A. 7 2018
6 8 232596711878804 2325-9671 10.1177/2325967118788045
Does the FIFA 11+ injury prevention program reduce the incidence of ACL injury in male soccer players? Clin Orthop Silvers-Granelli Holly J. Bizzini Mario Arundale Amelia Mandelbaum Bert R. Snyder-Mackler Lynn 10 2017
475 10 2447 2455 0009-921X 10.1007/s11999-017-5342-5
Anterior cruciate ligament injury prevention training in female athletes: a systematic review of injury reduction and results of athletic performance tests Sports Health Noyes Frank R. Barber Westin Sue D. 2012
4 1 36–46 1941-7381 10.1177/1941738111430203 PMID: 23016067 23016067
The association between the acute:chronic workload ratio and injury and its application in team sports: a systematic review Sports Medicine Griffin Alan Kenny Ian C. Comyns Thomas M. Lyons Mark 3 2020
50 3 561 580 0112-1642 10.1007/s40279-019-01218-2 31691167
