“When can I play ___________ again?”

Such a simple question. Following an anterior cruciate ligament reconstruction (ACLR), this is the answer that everyone (clinician, patient, coach, and parent) wants to know. Unfortunately, this simple question does not have a simple answer.

With copious amounts of research devoted to this pathology, it would seem like an easy question to answer, but that is far from the reality. In a study of 100 soccer athletes, only 72% returned to sport following ACLR and at 7 year follow-up, only 36% were still playing (Brophy et al). This low return to sport percentage is not isolated to soccer players, as a similar study (McCullough et al) found that only 63% of high school and 67% of college-level american football players were able to return to sport. Even more concerning, there is a substantial number of patients that will have a revision or additional surgery. According to Hettrich et al, at a 6 year follow-up for 980 patients, 18.9% had additional surgical procedures performed on the same knee that initially underwent ACLR. That same study showed that 7.7% had a revision ACLR, while 6.4% had an ACLR on the opposite knee. A study published by Paterno et al, identified a significant injury rate in subjects who had previously suffered an ACL tear. This is especially evident in young females who have greater than a 25% incidence of ACL rupture in their first year back to competition. Why is this the current state of affairs with this injury, and what can we do to improve these outcomes?

Before determining when a patient is ready to return to their sports, it is first necessary to understand which biomechanical factors and faulty movement patterns may have contributed to their initial injury. In 2005, Hewett et al published a landmark study identifying biomechanical factors that can help predict initial rupture of the ACL. dynamic valgus In this study, 205 female athletes performed a jump-landing task, and 9 of these went on to rupture their ACL during the following season. During the jump-landing task, these nine female athletes demonstrated increased knee abduction at landing (8°), which translated to 2.5 times more than all the others who did not sustain an injury. Those who injured their ACL also produced 20% higher ground reaction force upon landing, which was potentially influenced by a decreased knee flexion angle upon landing. All these factors considered, individuals who are at risk for rupturing or re-rupturing their ACL demonstrate landing patterns that coincide with the typical dynamic valgus mechanism of injury. This work led to the refinement of recommended ACL rehabilitation protocols (Hewett et al). This thorough criterion-based protocol placed a major emphasis on the need for “ACL Prevention Programs” to serve as a model for the last phase of ACL reconstruction rehabilitation.

All this being said, how can we assess these risk factors in our patients? In general, there are two classes of functional testing that should be utilized prior to clearing someone to return to sport; proprioceptive/dynamic postural control and functional hop testing. Both of which play an integral role in assessing a patient’s ability to control dynamic valgus. This valgus is often associated with the development of lower extremity pathology (patellofemoral pain syndrome, iliotibial band syndrome, ACLR, ect.). These tests challenge patients to a threshold that can identify motor control, proprioception, and muscular strength/endurance deficits. These are factors that cannot be assessed accurately with the typical range of motion, manual muscle test, and Lachman testing that seems to be common practice with regards to return to play criteria.

There are many proprioceptive tests that can be utilized in the clinical setting, however there are two that should be included in any ACLR rehabilitation program. The first, and probably most well-known, is the star excursion balance test (SEBT). This test originally involved the subject balancing on one leg while reaching with the opposite limb in 8 different directions. The test has since been modified and aptly renamed the Y-Balance Test (YBT), as the only directions included are anterior, posterolateral, and posteromedial. These two variations of the test were examined in a systematic review by Gribble et al and were both found to have excellent reliability (YBT: intra-rater reliability = 0.85-0.89 and inter-rater-reliability = 0.97-1.00, SEBT: 0.78-0.96 and 0.81-0.93). In addition to being a reliable test, it is also very applicable to ACLR patients. Delahunt et al evaluated the difference between limbs of female athletes who have undergone ACLR with regards to the performance of the SEBT. These subjects were, on average, 2.9 years removed from surgery and still demonstrated significant asymmetry. Significant deficits were seen in both the posterolateral and posteromedial directions, while altered hip frontal, sagittal, and transverse plane kinematics were also evident during testing. To reinforce the significance of this asymmetry in performance and kinematic profile, Plisky et al found that basketball players with anterior right-to-left reach differences of more than 4 cm were 2.5 times more likely to sustain lower extremity injuries. More importantly they also found that girls with a composite reach score of less than 94% of their limb length were 6.5 times more likely to sustain a lower extremity injury. Regardless of whether you utilize the full SEBT or the shortened YBT, quantifying the potential faulty movement patterns that likely predisposed this individual to their initial injury is paramount to a successful return to sport.

Y-Balance Test

In addition to the use of the SEBT or YBT, the use of the lateral step-down test (LSDT) is integral to assessing each individual patient’s movement quality and resulting strength, range of motion, and/or motor control deficits. While there is not as much literature to support this specific test, it still provides a snapshot into the athlete’s ability to control stability at the knee in both the frontal and transverse planes. As diminished strength of the hip abductors and external rotators frequently accompany pathology of the lower extremity, this test provides information to help individualize a patient’s program. While the efficacy of this test’s ability to predict future injury has not been assessed, its reliability has. In a study conducted by Piva et al, the reliability of the LSDT was moderate (ICC= 0.67, Percent Agreement= 80%). Additionally, a more recent study by Boden et al determined that the interrater reliability of the LSDT was equal to 0.59 (fair agreement) and the percent agreement was 83%. While this test is not as well known as the previously mentioned proprioceptive tests, it still provides a simple, reliable way to qualitatively assess your patient’s postural control early in the rehabilitation process.

As your patient continues to progress through their rehabilitation, more functionally appropriate and demanding tests and measures should be implemented. Of particular interest, regardless of your patient’s sport, are four functional jump tests (single hop, X-hop, triple hop, and timed hop). Xergia et al found significant asymmetries in terms of performance on the functional hop test, lower extremity kinematics, and isokinetic strength testing when comparing individuals following ACLR to asymptomatic control subjects. The ACLR group demonstrated greater isokinetic knee extension deficits and greater performance asymmetry during all three functional hop tests in comparison to the control group at 6 and 9 months post-operatively. Hop Testing In agreement with these findings, Myers et al evaluated the percent asymmetry between the four different hop tests in subjects who had undergone ACLR and normal uninjured control subjects. Predictably, the ACLR group demonstrated statistically significant symmetry deficits in comparison to the control group. Average symmetries for the ACLR group only approached 92% for the single-leg hop, 91% for the triple-hop, 92% for the crossover hop, and 96% for the timed hop test, whereas the only test that did not reach 100% symmetry for the control group was the crossover hop test (97%). In addition to these studies, Schmitt et al found that individuals who demonstrated a greater level of quadriceps femoris strength also performed superiorly on hop testing and actually performed at the same level as uninjured control subjects. While these seem like excellent procedures to assess in the clinic, how do these functional tests translate to our patient’s ability to perform everyday functional activities? Di Stasi et al evaluated gait asymmetries between individuals who passed their return to sport criteria (isometric quadriceps strength test, 4 single-legged hop tests, and 2 self-report questionnaires) and those who failed at 6 months status-post ACLR. They found that athletes who demonstrate superior functional performance 6 months after ACL reconstruction may have fewer abnormal and asymmetrical gait behaviors than those who could not pass the testing battery.

The need to ensure our patient’s ability to return to play at a level that does not compromise their safety should be our primary goal as clinicians, but are we actually using this information? The short answer is no. Barber-Westin et al conducted a systematic review of the return to sport criteria within the current research literature. Of the 264 studies included, 105 (40%) provided no criteria of any kind to release patients, 84 (32%) only relied on time since surgery, and 40 (15%) relied on time since surgery and subjective criteria. All in all, only 35% of studies included objective measures in their rationale for releasing their patients to their sport. This past year, a survey and subsequent analysis was conducted by Peterson et al in order to determine the current practice patterns of orthopedic surgeons with regards to return to sport. Unfortunately, this study yielded similar results. Of the 221 experienced arthroscopic surgeons surveyed, only ~40% utilized some sort of proprioceptive test, muscular strength analysis, or even the single-leg hop test.

“Only 35% of studies provided objective criteria to determine release of patients back to sport!”

Rehabilitation following ACLR should not be based upon specific time frames, but instead upon the achievement of specific criteria. This should dictate progression to the next stage. Time does not heal all wounds. These wounds must be treated with an efficacious program structured towards the specific demands of his/her sport and the underlying deficits that resulted in the initial injury. Terry Malone’s course, “ACL and PCL Injuries, Surgeries, and Rehabilitation” and Phil Plisky’s course, “Return to Sport and Discharge Planning”, provide many excellent clinical pearls that clinicians should look to implement within their treatment plans and eventual discharge planning.

While we cannot control all of the factors that affect a patient’s rehabilitation (psychological profile, concomitant injuries, level of competition, ect.), we can provide them with a safe, reliable, and effective plan guided by the use of specific and relevant tests and measures. We need to embrace the need to appropriately assess how each patient moves and any deficits that need to be addressed prior to releasing them to their respective sport. We only provide a disservice if they are released to play at 6 months only to re-injure themselves at 9 months. It is our responsibility to release them only when they can appropriately handle the stresses of their sport, rather than on a specific time frame or when they have a 5/5 grade on a manual muscle test.

So, do you agree or disagree? I would love to hear some feedback as to what you need to see before releasing an athlete to their sport…

Continued Reading…


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  1. Great article. Re-educating movement patterns is key! I suffered w a knee injury as a kid, and got useless rehab advice at the time. I finally sorted out the underlying movement issues in my late 20’s. My experience is why I do what I do today: training people to integrate & organize their movement into healthy, functional and sustainable patterns. Thanks for this wonderful article!


  2. Great post John. I don’t think we can ignore the healing stages of the graft as we know it’s still not 100% a year out, but basing our rehab off these functional outcome measures is extremely important. Do you think we should use these outcome measure for return to sport-related activities or competition? I’ve noticed quite a difference between return to competition and return to pre-injury levels. Keep up the great work.


  3. there is an interesting Delphi study published in 2012, Baker T, Haines S, Donaldson M. Development of a Physical Performance Assessment Instrument for Patients Who Sustained a Lower Extremity Injury in Preparation for Return to Sport: A Delphi Study. Ohio Physical Therapy Association Research Symposium. Oct. 2012
    which comments on the subject of return to sport. There are some limitations but it is a pilot study and is worth discussing.


  4. From personal experience I would say education plays a crucial role. I tore my ACL in my 20’s, had it repaired, ran a race 6 months later and cried b/c I was so happy. I’ve also gotten back to playing volleyball (which is how I tore it) and I would say I am better than ever.

    Two things – I wish that back in high school my coach was more aware of the mechanics of squats and proper jump landing (as well as diving to the ground to reach balls). I believe many girls get bad habits that early on which aggravate our tendencies for knee abduction upon landing.

    Second, I had rehab after my ACL but I don’t think I understood the magnitude of everything that needed correction. As a young professional I wasn’t patient and I didn’t have the funds to get a personal trainer after rehab which is what I should have done to properly strengthen my leg. So education after rehab to get the full function and strength back


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