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Rehabilitation and Return to Sport Testing After Anterior Cruciate Ligament Reconstruction: Where Are We in 2022?

      Abstract

      Athletes who sustain an anterior cruciate ligament (ACL) injury often opt for an ACL reconstruction (ACLR) with the goal and expectation to return to sports at the preinjury level. The proportion of athletes who successfully return to preinjury-level sport is low and disappointing, whereas the rate of second ACL injury in athletes under the age of 20 has been reported to be as high as 40% after return to sport (RTS). Although in recent years, new insights pertaining to RTS have been published, the lack of validity of RTS criteria after ACLR remain. The purpose of this clinical commentary is to present a critical overview of the current literature on RTS testing after ACLR.
      An injury of the anterior cruciate ligament (ACL) is a common injury in athletes participating in landing- and pivoting-type sports. An ACL reconstruction (ACLR) is considered by many the clinical standard to restore mechanical stability of the joint as a prerequisite for return to sports (RTS).
      • Marx R.G.
      • Jones E.C.
      • Angel M.
      • Wickiewicz T.L.
      • Warren R.F.
      Beliefs and attitudes of members of the American Academy of Orthopaedic Surgeons regarding the treatment of anterior cruciate ligament injury.
      Webster and Feller
      • Webster K.E.
      • Feller J.A.
      Expectations for return to preinjury sport before and after anterior cruciate ligament reconstruction.
      recently determined that patients who were about to undergo a primary ACLR had high expectations for return to their preinjury level of sport, with 88% expecting to achieve this outcome. In reality, only 65% of patients after ACLR return to their preinjury level of sport.
      • Ardern C.L.
      • Taylor N.F.
      • Feller J.A.
      • Webster K.E.
      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.
      Unfortunately, the active, young athlete (<20 years) who resumes activity after ACLR has a greater risk for a second ACL injury. Injury rates in this young cohort have been reported to be up to 23% to 29% in the literature.
      • Paterno M.V.
      • Rauh M.J.
      • Schmitt L.C.
      • Ford K.R.
      • Hewett T.E.
      Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport.
      • Webster K.E.
      • Feller J.A.
      • Leigh W.B.
      • Richmond A.K.
      Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction.
      • Webster K.E.
      • Feller J.A.
      Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction.
      In men’s Australian football, second ACL injury rates of 40% after RTS have recently been reported.
      • Webster K.E.
      • Hewett T.E.
      • Feller J.A.
      Anterior cruciate ligament injuries in Australian rules football: Incidence, prevention and return to play outcomes.
      There has consequently been a growth in studies that propose RTS criteria with the aim to reduce the risk of a second ACL injury. Despite the development of RTS guidelines over recent years, there is a lack of a scientific consensus on the RTS criteria used to release a patient to unrestricted sport activity after ACLR.
      • Dingenen B.
      • Gokeler A.
      Optimization of the return-to-sport paradigm after anterior cruciate ligament reconstruction: A critical step back to move forward.
      A proportional meta-analysis showed that only 23% of patients after ACLR passed RTS test batteries before RTS.
      • Webster K.E.
      • Hewett T.E.
      What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis.
      These findings highlight that many patients may have returned to sport without acceptable knee function. Although passing RTS criteria reduce the risk of subsequent graft rupture by 60%, it increases the risk of a contralateral ACL rupture by 235%.
      • Webster K.E.
      • Hewett T.E.
      What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis.
      In support of this meta-analysis, a recent study found that RTS tests including strength, hop tests, and patient-reported outcomes fail to identify patients who are at risk for a second ACL injury.
      • Welling W.
      • Benjaminse A.
      • Lemmink K.
      • Gokeler A.
      Passing return to sports tests after ACL reconstruction is associated with greater likelihood for return to sport but fail to identify second injury risk.
      Overall, the validity of current RTS tests is questionable. These equivocal findings in terms of validity of RTS tests after ACLR leaves clinicians with high level of uncertainty in clinical decision-making. The purpose of this clinical commentary is to present a critical overview of the current literature on RTS testing after ACLR.

      Definition of RTS tests

      Although the specific content of reported RTS test batteries has varied, overall they are designed to incorporate several domains of risk factors. An RTS test battery should at least include strength tests, hop tests, and measures of quality of movement.
      • van Melick N.
      • van Cingel R.E.
      • Brooijmans F.
      • et al.
      Evidence-based clinical practice update: Practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus.
      More recently, the importance of athletes’ psychological responses to the initial injury, to surgery, and to recovery during rehabilitation are important additional determinants of RTS.
      • Truong L.K.
      • Mosewich A.D.
      • Holt C.J.
      • Le C.Y.
      • Miciak M.
      • Whittaker J.L.
      Psychological, social and contextual factors across recovery stages following a sport-related knee injury: A scoping review.
      In the following sections we will discuss the various components that compromise the current recommended RTS test battery.

      Muscle Strength

      In the United States, 56% of therapists use manual muscle testing as their only method of strength evaluation.
      • Greenberg E.M.
      • Greenberg E.T.
      • Albaugh J.
      • Storey E.
      • Ganley T.J.
      Rehabilitation practice patterns following anterior cruciate ligament reconstruction: A survey of physical therapists.
      This is an area of concern because manual muscle tests using the Medical Research Council scale has several limitations, including poorly defined limits between grades “4” and “5.”
      • O’Neill S.
      • Jaszczak S.L.T.
      • Steffensen A.K.S.
      • Debrabant B.
      Using 4+ to grade near-normal muscle strength does not improve agreement.
      For research purposes, isokinetic dynamometry is often used for strength assessment of the quadriceps and hamstrings.
      • Logerstedt D.S.
      • Snyder-Mackler L.
      • Ritter R.C.
      • Axe M.J.
      • Godges J.J.
      Knee stability and movement coordination impairments: Knee ligament sprain.
      However, isokinetic devices lack practicality in clinical settings because of high cost, lack of portability, and space requirements. A more clinically viable alternative is hand-held dynamometry
      • Kim S.-G.
      • Lee Y.-S.
      The intra- and inter-rater reliabilities of lower extremity muscle strength assessment of healthy adults using a hand held dynamometer.
      or the use of, for example, a leg press or leg extension machine.
      • Nagai T.
      • Schilaty N.D.
      • Laskowski E.R.
      • Hewett T.E.
      Hop tests can result in higher limb symmetry index values than isokinetic strength and leg press tests in patients following ACL reconstruction.
      Commonly a limb symmetry index (LSI) is used, defined as the ratio of the involved limb score and the uninvolved limb score expressed in percent ((involved/uninvolved) · 100). An LSI > 90% is usually used as a cutoff score.
      • Lynch A.D.
      • Logerstedt D.S.
      • Grindem H.
      • et al.
      Consensus criteria for defining “successful outcome” after ACL injury and reconstruction: A Delaware-Oslo ACL cohort investigation.
      For recreational and non-pivoting sports an LSI of >90% may be acceptable, whereas a >100% LSI for knee extensor and knee flexor muscle strength for the pivoting/contact/competitive athlete has been recommended.
      • Thomeé R.
      • Kaplan Y.
      • Kvist J.
      • et al.
      Muscle strength and hop performance criteria prior to return to sports after ACL reconstruction.
      A few major issues arise when using these criteria: 1) only 14% of all patients achieved a LSI of 100% for strength tests at 2 years after ACLR
      • Thomeé R.
      • Neeter C.
      • Gustavsson A.
      • et al.
      Variability in leg muscle power and hop performance after anterior cruciate ligament reconstruction.
      questioning whether this is feasible in daily practice; 2) the LSI is based on the assumption that the uninjured leg can be used as a reference for strength. Larsen et al.
      • Larsen J.B.
      • Farup J.
      • Lind M.
      • Dalgas U.
      Muscle strength and functional performance is markedly impaired at the recommended time point for sport return after anterior cruciate ligament reconstruction in recreational athletes.
      showed that, not only do patients after ACLR exhibit side to side deficits, but the uninvolved limb of ACLR is also significantly weaker to a matched limb of a control group. This implies that the LSI may underestimate strength deficits and argues for an implementation of absolute strength evaluation and not only limb symmetry.
      • Larsen J.B.
      • Farup J.
      • Lind M.
      • Dalgas U.
      Muscle strength and functional performance is markedly impaired at the recommended time point for sport return after anterior cruciate ligament reconstruction in recreational athletes.
      Current evidence summarized in a meta-analysis revealed persistent quadriceps and hamstring strength deficits in both the short (<6 months) and long term (>2 years) after ACL injury.
      • Tayfur B.
      • Charuphongsa C.
      • Morrissey D.
      • Miller S.C.
      Neuromuscular function of the knee joint following knee injuries: Does it ever get back to normal? A systematic review with meta-analyses.
      In that meta-analysis, studies comparing the strength on the involved side with the uninvolved side were excluded because there was evidence of bilateral neuromuscular changes after unilateral injury.
      • Tayfur B.
      • Charuphongsa C.
      • Morrissey D.
      • Miller S.C.
      Neuromuscular function of the knee joint following knee injuries: Does it ever get back to normal? A systematic review with meta-analyses.
      Most studies report assessment of maximal strength; however, this may only present the tip of the iceberg of strength deficits after ACLR. Deficits in rate of force development, power, and reactive strength have been reported as well, which may have important relationships with athletic performance and second ACL injury prevention rather than maximal strength alone.
      • Maestroni L.
      • Read P.
      • Turner A.
      • Korakakis V.
      • Papadopoulos K.
      Strength, rate of force development, power and reactive strength in adult male athletic populations post anterior cruciate ligament reconstruction—A systematic review and meta-analysis.

      Hop Tests

      Commonly used hop tests are the single hop for distance, triple hop for distance, triple cross-over hop, and the 6-m timed hop.
      • Logerstedt D.S.
      • Scalzitti D.
      • Risberg M.A.
      • et al.
      Knee stability and movement coordination impairments: Knee ligament sprain revision 2017.
      LSI criteria >90% could be used as cutoff scores to determine readiness for RTS in recreational or nonpivoting-type sports, whereas an LSI of 100% is recommended for pivoting/contact sports.
      • Thomeé R.
      • Kaplan Y.
      • Kvist J.
      • et al.
      Muscle strength and hop performance criteria prior to return to sports after ACL reconstruction.
      As with the LSI for strength, there are some concerns regarding the use of the uninvolved limb as a reference for the involved limb. Athletes who have undergone an ACLR demonstrate bilateral deficits on hop tests in comparison to age- and sex-matched normative data of healthy controls.
      • Gokeler A.
      • Welling W.
      • Benjaminse A.
      • Lemmink K.
      • Seil R.
      • Zaffagnini S.
      A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: A case control study.
      Of interest, all athletes in that study had a mean LSI of 95.4% for the 3 hop tests, being well over the clinical cutoff of 90% symmetry frequently used for RTS criteria.
      • Gokeler A.
      • Welling W.
      • Benjaminse A.
      • Lemmink K.
      • Seil R.
      • Zaffagnini S.
      A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: A case control study.
      Despite achieving an LSI >90%, patients demonstrated significant and clinical relevant deficits in performance for both limbs when compared to normative data from healthy athletes. Findings from a recent meta-analysis suggest that symmetry in hop distance may not mean knee function is also symmetrical.
      • Kotsifaki A.
      • Whiteley R.
      • Van Rossom S.
      • et al.
      Single leg hop for distance symmetry masks lower limb biomechanics: Time to discuss hop distance as decision criterion for return to sport after ACL reconstruction? [published online March 9, 2021]. Br J Sports Med.
      Moreover, the LSI should not be used in isolation to evaluate functional performance changes after ACLR, because it may overestimate functional improvement, as a result of worsening contralateral limb function.
      • Patterson B.E.
      • Crossley K.M.
      • Perraton L.G.
      • et al.
      Limb symmetry index on a functional test battery improves between one and five years after anterior cruciate ligament reconstruction, primarily due to worsening contralateral limb function.
      Using the LSI for hop tests may underestimate performance deficits and should therefore be used with caution as a criterion for RTS after ACLR.
      • Gokeler A.
      • Welling W.
      • Benjaminse A.
      • Lemmink K.
      • Seil R.
      • Zaffagnini S.
      A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: A case control study.
      ,
      • Wellsandt E.
      • Failla M.J.
      • Snyder-Mackler L.
      Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury.
      ,
      • Kotsifaki A.
      • Korakakis V.
      • Whiteley R.
      • Van Rossom S.
      • Jonkers I.
      Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: A systematic review and meta-analysis.
      On a final note, a limitation of the current hop test battery is that these tests predominantly consist of straight movements in the forward direction. Medial and rotational hop tests are more likely to show limb asymmetries in athletes after ACLR participants compared to forward hop tests.
      • Dingenen B.
      • Truijen J.
      • Bellemans J.
      • Gokeler A.
      Test–retest reliability and discriminative ability of forward, medial and rotational single-leg hop tests.

      Movement Quality Assessment

      Although patients after ACLR may achieve normalization in single leg hop test distance, kinematic and kinetic deficits may persist.
      • Kotsifaki A.
      • Korakakis V.
      • Whiteley R.
      • Van Rossom S.
      • Jonkers I.
      Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: A systematic review and meta-analysis.
      Welling et al.
      • Welling W.
      • Benjaminse A.
      • Seil R.
      • Lemmink K.
      • Gokeler A.
      Altered movement during single leg hop test after ACL reconstruction: Implications to incorporate 2-D video movement analysis for hop tests.
      found that 60% of patients after ACLR had abnormal landing kinematics in the injured leg compared to their noninjured leg, although 72.3% of them passed the LSI >90% criteria for hop tests. Between-limb deficits in eccentric and concentric loading parameters persist >9 months after ACLR, indicating a compensatory offloading strategy to protect the involved limb during an athletic performance task.
      • Read P.J.
      • Michael Auliffe S.
      • Wilson M.G.
      • Graham-Smith P.
      Lower limb kinetic asymmetries in professional soccer players with and without anterior cruciate ligament reconstruction: Nine months is not enough time to restore “functional” symmetry or return to performance.
      In addition, graft-specific loading asymmetries have been identified for double leg jump-landing tasks.
      • Miles J.J.
      • King E.
      • Falvey É.C.
      • Daniels K.A.J.
      Patellar and hamstring autografts are associated with different jump task loading asymmetries after ACL reconstruction.
      Greater asymmetry of trunk-side flexion, distance from center of mass to the knee and ankle in the frontal plane, pelvic tilt, and pelvic drop during unplanned change of direction was found for those athletes who sustained second ACL injuries compared to this who did not.
      • King E.
      • Richter C.
      • Daniels K.A.J.
      • et al.
      Biomechanical but not strength or performance measures differentiate male athletes who experience ACL reinjury on return to level 1 sports.
      Therefore the integration of a biomechanical evaluation should supplement the decision-making regarding RTS.

      Psychological factors

      An ACL injury not only leads to physical impairments but also has a psychological impact. Hence, in addition to the physical readiness, monitoring patient-reported outcome measures and psychological readiness are important to determine successful RTS. Significantly lower scores on self-reported knee function questionnaires were found in patients who did not RTS compared to patients who RTS.
      • Ardern C.L.
      • Taylor N.F.
      • Feller J.A.
      • Whitehead T.S.
      • Webster K.E.
      Sports participation 2 years after anterior cruciate ligament reconstruction in athletes who had not returned to sport at 1 year: A prospective follow-up of physical function and psychological factors in 122 athletes.
      Psychological readiness is a predictor for returning to preinjury levels of sport in patients after ACLR.
      • Ardern C.L.
      • Taylor N.F.
      • Feller J.A.
      • Whitehead T.S.
      • Webster K.E.
      Psychological responses matter in returning to preinjury level of sport after anterior cruciate ligament reconstruction surgery.
      A systematic review revealed that 65% of patients cited a psychological reason for not returning to sport, with fear of reinjury as the most common reason.
      • Nwachukwu B.U.
      • Adjei J.
      • Rauck R.C.
      • et al.
      How much do psychological factors affect lack of return to play after anterior cruciate ligament reconstruction? A systematic review.
      In other words, patients with higher scores on questionnaires regarding psychological readiness for RTS had increased chances to return to the preinjury level of sport.

      Rehabilitative Approach

      RTS tests should be seen in the context of factors such as content, specificity, intensity, frequency, and duration of rehabilitation given the need for optimization of current rehabilitation programs. Several conceptual frameworks on how rehabilitation can be optimized have been published but require scientific validation.
      • Dingenen B.
      • Gokeler A.
      Optimization of the return-to-sport paradigm after anterior cruciate ligament reconstruction: A critical step back to move forward.
      ,
      • Gokeler A.
      • Benjaminse A.
      • Hewett T.E.
      • et al.
      Feedback techniques to target functional deficits following anterior cruciate ligament reconstruction: Implications for motor control and reduction of second injury risk.
      ,
      • Gokeler A.
      • Neuhaus D.
      • Benjaminse A.
      • Grooms D.R.
      • Baumeister J.
      Principles of motor learning to support neuroplasticity after ACL injury: Implications for optimizing performance and reducing risk of second ACL injury.
      In a retrospective study of 676 patients after ACLR, an individualized RTS rehabilitation program supervised by strength and conditioning coaches over a period of 3 months in addition to the standard rehabilitation program was the most important factor to positively influence an RTS test battery.
      • Franck F.
      • Saithna A.
      • Vieira T.D.
      • et al.
      Return to sport composite test after anterior cruciate ligament reconstruction (K-STARTS): Factors affecting return to sport test score in a retrospective analysis of 676 patients.
      This study is in agreement with previous studies.
      • Edwards P.K.
      • Ebert J.R.
      • Joss B.
      • et al.
      Patient characteristics and predictors of return to sport at 12 months after anterior cruciate ligament reconstruction: The importance of patient age and postoperative rehabilitation.
      ,
      • Della Villa F.
      • Andriolo L.
      • Ricci M.
      • et al.
      Compliance in post-operative rehabilitation is a key factor for return to sport after revision anterior cruciate ligament reconstruction.
      Patients who completed 6 months of rehabilitation incorporating jumping and agility tasks were almost 8 times more likely to RTS compared with those who did not.
      • Edwards P.K.
      • Ebert J.R.
      • Joss B.
      • et al.
      Patient characteristics and predictors of return to sport at 12 months after anterior cruciate ligament reconstruction: The importance of patient age and postoperative rehabilitation.
      Della Villa et al.
      • Della Villa F.
      • Andriolo L.
      • Ricci M.
      • et al.
      Compliance in post-operative rehabilitation is a key factor for return to sport after revision anterior cruciate ligament reconstruction.
      evaluated the association between compliance in postoperative rehabilitation and RTS rate in patients after ACLR revision. As much as 86% of fully compliant patients were able to return to the preinjury level, versus 50% and 45% of the patients defined as minimally compliant and noncompliant, respectively.
      • Della Villa F.
      • Andriolo L.
      • Ricci M.
      • et al.
      Compliance in post-operative rehabilitation is a key factor for return to sport after revision anterior cruciate ligament reconstruction.

      Timing of RTS testing?

      It has been suggested to delay RTS until 9 months after ACLR surgery.
      • Grindem H.
      • Snyder-Mackler L.
      • Moksnes H.
      • Engebretsen L.
      • Risberg M.A.
      Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: The Delaware-Oslo ACL cohort study.
      However, the claimed 84% reduction of risk was a nonsignificant finding because of low statistical power.
      • Grindem H.
      • Snyder-Mackler L.
      • Moksnes H.
      • Engebretsen L.
      • Risberg M.A.
      Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: The Delaware-Oslo ACL cohort study.
      Between 9 months and 2 years after surgery, there was no significant reduction in the risk for second knee injuries. Over that time period, 19.4% of these patients sustained second knee reinjuries.
      • Grindem H.
      • Snyder-Mackler L.
      • Moksnes H.
      • Engebretsen L.
      • Risberg M.A.
      Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: The Delaware-Oslo ACL cohort study.
      In a recent study no clear association between age and second ACL injury was suggested.
      • Grindem H.
      • Engebretsen L.
      • Axe M.
      • Snyder-Mackler L.
      • Risberg M.A.
      Activity and functional readiness, not age, are the critical factors for second anterior cruciate ligament injury—The Delaware-Oslo ACL cohort study.
      This is in conflict with other studies. Webster et al.
      • Webster K.E.
      • Feller J.A.
      • Leigh W.B.
      • Richmond A.K.
      Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction.
      reviewed 561 patients at a mean follow-up of approximately 5 years and reported odds for sustaining a contralateral ACL rupture increased threefold for patients younger than 20 years. Kaeding et al.
      • Kaeding C.C.
      • Pedroza A.D.
      • Reinke E.K.
      • et al.
      Risk factors and predictors of subsequent ACL injury in either knee after ACL reconstruction.
      reviewed 2683 patients from the Multicenter Orthopaedic Outcomes Network cohort and reported that younger age and higher activity level (and allograft type) were predictors of increased odds of ipsilateral graft failure. It may be questioned whether young age is indeed a risk factor or a proxy for higher exposure to high-risk activities such as return to soccer or other landing and pivoting sports.
      Future studies should clearly point out whether tests were conducted at a certain fixed time point (for example 9 months after surgery) or at the time of return to sport. If the second option would be the case, it should be clear which criteria were used to decide whether it’s safe to return to sport.

      How Many Tests Need to Be Included?

      Another problem with these test batteries is the “penalty” of multiple tests. With a test battery, multiple tests across several domains are required to be passed at a required pass rate, which was most often set at 90%. If athletes meet the pass rate for one test and a second test with a 90% pass requirement is added, the percentage of athletes who pass will almost certainly drop.
      • Toole A.R.
      • Ithurburn M.P.
      • Rauh M.J.
      • Hewett T.E.
      • Paterno M.V.
      • Schmitt L.C.
      Young athletes after anterior cruciate ligament reconstruction cleared for sports participation: How many actually meet recommended return-to-sport criteria cutoffs?.
      For example, even if 80% of athletes pass each test of a test battery, the overall pass rate for the test battery will be dependent on the total number of tests such that the pass rate for the first test will be 80%, but then only 64% (0.8 × 0.8) for 2 tests, 51% (0.64 × 0.8) for 3, 40% (0.5 × 0.8) for 4, and so on.
      • Hewett T.E.
      • Webster K.E.
      • Hurd W.J.
      Systematic selection of key logistic regression variables for risk prediction analyses: A five-factor maximum model.
      Furthermore, the relative importance of each of these tests is unknown and can vary between sports and individuals.

      What Are the Consequences of the RTS Testing?

      The consequence of not passing tests, is often not explicitly stated in studies. In the study of Grindem et al.,
      • Grindem H.
      • Snyder-Mackler L.
      • Moksnes H.
      • Engebretsen L.
      • Risberg M.A.
      Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: The Delaware-Oslo ACL cohort study.
      of the 74 patients who returned to level 1 sports, those 51 patients who did not sustain a second knee injury had a mean quadriceps LSI of 84.4%, which was below the recommended LSI of >90%. In the review of Webster and Hewett,
      • Webster K.E.
      • Hewett T.E.
      What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis.
      77% of patients who did not pass RTS test after ACLR, participated in sports. On the one hand, the above findings highlight the need for a stricter definition of what the consequences of the tests are. On the other hand, the very low proportion of athletes passing the traditional RTS tests also indicate that in general, a criterion-based rehabilitation is not adopted in clinical practice.
      • Greenberg E.M.
      • Greenberg E.T.
      • Albaugh J.
      • Storey E.
      • Ganley T.J.
      Rehabilitation practice patterns following anterior cruciate ligament reconstruction: A survey of physical therapists.
      ,
      • Ebert J.R.
      • Webster K.E.
      • Edwards P.K.
      • et al.
      Current perspectives of Australian therapists on rehabilitation and return to sport after anterior cruciate ligament reconstruction: A survey.
      ,
      • Dingenen B.
      • Billiet B.
      • De Baets L.
      • Bellemans J.
      • Truijen J.
      • Gokeler A.
      Rehabilitation strategies of Flemish physical therapists before and after anterior cruciate ligament reconstruction: An online survey.
      The problem within the current literature is that we hardly know what happened after the RTS tests. The exposure to high-risk activities is an essential point when evaluating the validity of RTS tests. Indeed, a player failing RTS tests but returning to sports with very low exposure to high-risk activities might still be at a relatively lower injury risk compared to another player passing RTS tests with very high exposure to high-risk activities. However, this exposure is not reported in current studies. The use of the term RTS must be accompanied by a detailed description of the individual characteristics of the athletes being studied; the intensity, duration, and frequency of each exposure; duration of sport participation after ACLR; the type and level of activity; and the use of protective equipment.
      • Dingenen B.
      • Gokeler A.
      Optimization of the return-to-sport paradigm after anterior cruciate ligament reconstruction: A critical step back to move forward.
      Truly successful RTS allows the athlete to return to their prior level of sport while also at a reduced (or reasonable) risk for a second ACL (or any) injury.
      • Webster K.E.
      • Hewett T.E.
      What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis.

      Conclusion

      After ACLR, ligament (ACL), the proportion of athletes who successfully return to pre-injury level sport is low and disappointing, while the rate of second ACL injury in athletes under the age of 20 has been reported to be as high as 40% after RTS. Although in recent years, new insights pertaining RTS have been published, the lack of validity of RTS criteria after ACLR remains.

      Supplementary Data

      References

        • Marx R.G.
        • Jones E.C.
        • Angel M.
        • Wickiewicz T.L.
        • Warren R.F.
        Beliefs and attitudes of members of the American Academy of Orthopaedic Surgeons regarding the treatment of anterior cruciate ligament injury.
        Arthroscopy. 2003; 19: 762-770
        • Webster K.E.
        • Feller J.A.
        Expectations for return to preinjury sport before and after anterior cruciate ligament reconstruction.
        Am J Sports Med. 2019; 47: 578-583https://doi.org/10.1177/0363546518819454
        • Ardern C.L.
        • Taylor N.F.
        • Feller J.A.
        • Webster K.E.
        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 Sport Med. 2014; 48: 1543-1552
        • Paterno M.V.
        • Rauh M.J.
        • Schmitt L.C.
        • Ford K.R.
        • Hewett T.E.
        Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport.
        Am J Sports Med. 2014; 42: 1567-1573
        • Webster K.E.
        • Feller J.A.
        • Leigh W.B.
        • Richmond A.K.
        Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction.
        Am J Sport Med. 2014; 42: 641-647
        • Webster K.E.
        • Feller J.A.
        Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction.
        Am J Sport Med. 2016; 44: 2827-2832
        • Webster K.E.
        • Hewett T.E.
        • Feller J.A.
        Anterior cruciate ligament injuries in Australian rules football: Incidence, prevention and return to play outcomes.
        Open Access J Sport Med. 2021; 12: 33-41
        • Dingenen B.
        • Gokeler A.
        Optimization of the return-to-sport paradigm after anterior cruciate ligament reconstruction: A critical step back to move forward.
        Sport Med. 2017; 47: 1487-1500
        • Webster K.E.
        • Hewett T.E.
        What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis.
        Sport Med. 2019; 49: 917-929
        • Welling W.
        • Benjaminse A.
        • Lemmink K.
        • Gokeler A.
        Passing return to sports tests after ACL reconstruction is associated with greater likelihood for return to sport but fail to identify second injury risk.
        Knee. 2020; 27: 949-957
        • van Melick N.
        • van Cingel R.E.
        • Brooijmans F.
        • et al.
        Evidence-based clinical practice update: Practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus.
        Br J Sport Med. 2016; 50: 1506-1515
        • Truong L.K.
        • Mosewich A.D.
        • Holt C.J.
        • Le C.Y.
        • Miciak M.
        • Whittaker J.L.
        Psychological, social and contextual factors across recovery stages following a sport-related knee injury: A scoping review.
        Br J Sports Med. 2020; 54: 1149-1156
        • Greenberg E.M.
        • Greenberg E.T.
        • Albaugh J.
        • Storey E.
        • Ganley T.J.
        Rehabilitation practice patterns following anterior cruciate ligament reconstruction: A survey of physical therapists.
        J Orthop Sport Phys Ther. 2018; 48: 801-811
        • O’Neill S.
        • Jaszczak S.L.T.
        • Steffensen A.K.S.
        • Debrabant B.
        Using 4+ to grade near-normal muscle strength does not improve agreement.
        Chiropr Man Ther. 2017; 25: 1-9
        • Logerstedt D.S.
        • Snyder-Mackler L.
        • Ritter R.C.
        • Axe M.J.
        • Godges J.J.
        Knee stability and movement coordination impairments: Knee ligament sprain.
        J Orthop Sport Phys Ther. 2010; 40: A1-A37
        • Kim S.-G.
        • Lee Y.-S.
        The intra- and inter-rater reliabilities of lower extremity muscle strength assessment of healthy adults using a hand held dynamometer.
        J Phys Ther Sci. 2015; 27: 1799-1801
        • Nagai T.
        • Schilaty N.D.
        • Laskowski E.R.
        • Hewett T.E.
        Hop tests can result in higher limb symmetry index values than isokinetic strength and leg press tests in patients following ACL reconstruction.
        Knee Surgery, Sport Traumatol Arthrosc. 2020; 28: 816-822
        • Lynch A.D.
        • Logerstedt D.S.
        • Grindem H.
        • et al.
        Consensus criteria for defining “successful outcome” after ACL injury and reconstruction: A Delaware-Oslo ACL cohort investigation.
        Br J Sport Med. 2015; 49: 335-342
        • Thomeé R.
        • Kaplan Y.
        • Kvist J.
        • et al.
        Muscle strength and hop performance criteria prior to return to sports after ACL reconstruction.
        Knee Surgery, Sport Traumatol Arthrosc. 2011; 19: 1798-1805
        • Thomeé R.
        • Neeter C.
        • Gustavsson A.
        • et al.
        Variability in leg muscle power and hop performance after anterior cruciate ligament reconstruction.
        Knee Surgery, Sport Traumatol Arthrosc. 2012; 20: 1143-1151
        • Larsen J.B.
        • Farup J.
        • Lind M.
        • Dalgas U.
        Muscle strength and functional performance is markedly impaired at the recommended time point for sport return after anterior cruciate ligament reconstruction in recreational athletes.
        Hum Mov Sci. 2015; 39: 73-87
        • Tayfur B.
        • Charuphongsa C.
        • Morrissey D.
        • Miller S.C.
        Neuromuscular function of the knee joint following knee injuries: Does it ever get back to normal? A systematic review with meta-analyses.
        Sport Med. 2021; 51: 321-338
        • Maestroni L.
        • Read P.
        • Turner A.
        • Korakakis V.
        • Papadopoulos K.
        Strength, rate of force development, power and reactive strength in adult male athletic populations post anterior cruciate ligament reconstruction—A systematic review and meta-analysis.
        Phys Ther Sport. 2021; 47: 91-104
        • Logerstedt D.S.
        • Scalzitti D.
        • Risberg M.A.
        • et al.
        Knee stability and movement coordination impairments: Knee ligament sprain revision 2017.
        J Orthop Sport Phys Ther. 2017; 47: A1-A47
        • Gokeler A.
        • Welling W.
        • Benjaminse A.
        • Lemmink K.
        • Seil R.
        • Zaffagnini S.
        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. 2017; 103: 947-951
        • Kotsifaki A.
        • Whiteley R.
        • Van Rossom S.
        • et al.
        Single leg hop for distance symmetry masks lower limb biomechanics: Time to discuss hop distance as decision criterion for return to sport after ACL reconstruction? [published online March 9, 2021]. Br J Sports Med.
        • Patterson B.E.
        • Crossley K.M.
        • Perraton L.G.
        • et al.
        Limb symmetry index on a functional test battery improves between one and five years after anterior cruciate ligament reconstruction, primarily due to worsening contralateral limb function.
        Phys Ther Sport. 2020; 44: 67-74
        • Wellsandt E.
        • Failla M.J.
        • Snyder-Mackler L.
        Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury.
        J Orthop Sport Phys Ther. 2017; : 1-18
        • Kotsifaki A.
        • Korakakis V.
        • Whiteley R.
        • Van Rossom S.
        • Jonkers I.
        Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: A systematic review and meta-analysis.
        Br J Sports Med. 2020; 54: 139-153
        • Dingenen B.
        • Truijen J.
        • Bellemans J.
        • Gokeler A.
        Test–retest reliability and discriminative ability of forward, medial and rotational single-leg hop tests.
        Knee. 2019; 26: 978-987
        • Welling W.
        • Benjaminse A.
        • Seil R.
        • Lemmink K.
        • Gokeler A.
        Altered movement during single leg hop test after ACL reconstruction: Implications to incorporate 2-D video movement analysis for hop tests.
        Knee Surg Sport Traumatol Arthrosc. 2018; 26: 3012-3019
        • Read P.J.
        • Michael Auliffe S.
        • Wilson M.G.
        • Graham-Smith P.
        Lower limb kinetic asymmetries in professional soccer players with and without anterior cruciate ligament reconstruction: Nine months is not enough time to restore “functional” symmetry or return to performance.
        Am J Sports Med. 2020; 48: 1365-1373
        • Miles J.J.
        • King E.
        • Falvey É.C.
        • Daniels K.A.J.
        Patellar and hamstring autografts are associated with different jump task loading asymmetries after ACL reconstruction.
        Scand J Med Sci Sport. 2019; 29: 1212-1222
        • King E.
        • Richter C.
        • Daniels K.A.J.
        • et al.
        Biomechanical but not strength or performance measures differentiate male athletes who experience ACL reinjury on return to level 1 sports.
        Am J Sports Med. 2021; 49: 918-927
        • Ardern C.L.
        • Taylor N.F.
        • Feller J.A.
        • Whitehead T.S.
        • Webster K.E.
        Sports participation 2 years after anterior cruciate ligament reconstruction in athletes who had not returned to sport at 1 year: A prospective follow-up of physical function and psychological factors in 122 athletes.
        Am J Sport Med. 2015; 43: 848-856
        • Ardern C.L.
        • Taylor N.F.
        • Feller J.A.
        • Whitehead T.S.
        • Webster K.E.
        Psychological responses matter in returning to preinjury level of sport after anterior cruciate ligament reconstruction surgery.
        Am J Sport Med. 2013; 41: 1549-1558
        • Nwachukwu B.U.
        • Adjei J.
        • Rauck R.C.
        • et al.
        How much do psychological factors affect lack of return to play after anterior cruciate ligament reconstruction? A systematic review.
        Orthop J Sport Med. 2019; 7: 1-7
        • Gokeler A.
        • Benjaminse A.
        • Hewett T.E.
        • et al.
        Feedback techniques to target functional deficits following anterior cruciate ligament reconstruction: Implications for motor control and reduction of second injury risk.
        Sport Med. 2013; 43: 1065-1074
        • Gokeler A.
        • Neuhaus D.
        • Benjaminse A.
        • Grooms D.R.
        • Baumeister J.
        Principles of motor learning to support neuroplasticity after ACL injury: Implications for optimizing performance and reducing risk of second ACL injury.
        Sport Med. 2019; 49: 853-865
        • Franck F.
        • Saithna A.
        • Vieira T.D.
        • et al.
        Return to sport composite test after anterior cruciate ligament reconstruction (K-STARTS): Factors affecting return to sport test score in a retrospective analysis of 676 patients.
        Sport Health. 2021; 13: 364-372
        • Edwards P.K.
        • Ebert J.R.
        • Joss B.
        • et al.
        Patient characteristics and predictors of return to sport at 12 months after anterior cruciate ligament reconstruction: The importance of patient age and postoperative rehabilitation.
        Orthop J Sport Med. 2018; 6 (232596711879757)
        • Della Villa F.
        • Andriolo L.
        • Ricci M.
        • et al.
        Compliance in post-operative rehabilitation is a key factor for return to sport after revision anterior cruciate ligament reconstruction.
        Knee Surg Sport Traumatol Arthrosc. 2020; 28: 463-469
        • Grindem H.
        • Snyder-Mackler L.
        • Moksnes H.
        • Engebretsen L.
        • Risberg M.A.
        Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: The Delaware-Oslo ACL cohort study.
        Br J Sports Med. 2016; 50: 804-808
        • Grindem H.
        • Engebretsen L.
        • Axe M.
        • Snyder-Mackler L.
        • Risberg M.A.
        Activity and functional readiness, not age, are the critical factors for second anterior cruciate ligament injury—The Delaware-Oslo ACL cohort study.
        Br J Sports Med. 2020; 54: 1099-1102
        • Kaeding C.C.
        • Pedroza A.D.
        • Reinke E.K.
        • et al.
        Risk factors and predictors of subsequent ACL injury in either knee after ACL reconstruction.
        Am J Sports Med. 2015; 43: 1583-1590
        • Toole A.R.
        • Ithurburn M.P.
        • Rauh M.J.
        • Hewett T.E.
        • Paterno M.V.
        • Schmitt L.C.
        Young athletes after anterior cruciate ligament reconstruction cleared for sports participation: How many actually meet recommended return-to-sport criteria cutoffs?.
        J Orthop Sport Phys Ther. 2017; 47: 1-27
        • Hewett T.E.
        • Webster K.E.
        • Hurd W.J.
        Systematic selection of key logistic regression variables for risk prediction analyses: A five-factor maximum model.
        Clin J Sport Med. 2019; 29: 78-85
        • Ebert J.R.
        • Webster K.E.
        • Edwards P.K.
        • et al.
        Current perspectives of Australian therapists on rehabilitation and return to sport after anterior cruciate ligament reconstruction: A survey.
        Phys Ther Sport. 2019; 35: 139-145
        • Dingenen B.
        • Billiet B.
        • De Baets L.
        • Bellemans J.
        • Truijen J.
        • Gokeler A.
        Rehabilitation strategies of Flemish physical therapists before and after anterior cruciate ligament reconstruction: An online survey.
        Phys Ther Sport. 2021; 49: 68-76