PT Classroom - Functional Testing for Return to Sport after Anterior Cruciate Ligament (ACL) Repair ׀ by  Amber Wacek, DPT


Amber Wacek, DPT received her doctor of physical therapy degree from the University of Wisconsin - Milwaukee in May of 2010. She plans to pursue a specialty in orthopedics in the near future. Amber is a physical therapist with United Hospital System in Kenosha where she works both in the inpatient acute and outpatient physical therapy settings.


 Functional Testing for Return to Sport after Anterior

Cruciate Ligament (ACL) Repair


The first question I often hear upon evaluation of an athlete following an ACL repair is, “When will I return to playing basketball/soccer/football?” The literature on when to send an athlete back to contact sports varies from 3-12 months (1). It becomes difficult to predict, as a clinician, on when likely return is, secondary to the many variables such as physician preference, the pt’s injury history, type of ACL repair, type of rehabilitation protocol, etc. to factor into your estimation. The numerous variables from individuality and the variance in the literature recommendations give little guidance to clinicians. The following article is meant to give clinicians a guide on clinical decision making for return to sport following ACL repair.

Typically, return to full involvement in sports, according to protocols is 6 months after surgery, and accelerated rehab programs allow their patients to return to full sport around 4 months (1). According to Kvist (2005), return to sport is the secondary goal, fulfilling the criteria of the protocol for return to sport is the primary goal.

Criteria for return to sport following ACL repair often includes full knee AROM, resolution of pain, no joint effusion present, and less than a 10% performance and strength deficits when compared to uninjured knee(1). There are often other measurements as well in literature including KT-1000 testing (anterior-posterior translation), and isokinetic testing. Both of these require expensive equipment that many clinics lack.

The performance aspect of the testing often uses single limb hop testing for distance. This area of outcome testing is meant to compare lower limbs for functional differences. Single limb hop tests have very low sensitivity to detect abnormal limb function. In ACL deficient knees (without repairs), 50% continue to perform normally in single limb hop tests (2). Although scores that demonstrate abnormality on single limb hop test are correlated with quad weakness, and self assess difficulty of pivoting, and twisting (2).

To increase testing sensitivity to abnormal function of lower extremities, Noyes et al., recommend using a battery of tests that they deemed as the Lower Limb Symmetry Index. This symmetry index includes single limb hop test, timed 6m hop test, triple hop for distance (single limb), and cross over hop for distance (see image below). This battery of tests have increased sensitivity, with 58% of ACL deficient knees scoring abnormally, which researchers defined as scoring 85% or less of the unaffected leg scored(2). The authors recommend using at least 2 of the above functional hop tests. These tests, unlike isokinetic and KT-1000 testing require very little equipment, space or time. Hop testing has been shown to be valid and reliable in multiple studies for healthy and injured participants (3,4). Note: Most ACL protocols do not allow jumping activities to begin until 16 weeks post operatively, and clinicians should consult either protocol or physician before performing these tests.

Calculating the Lower Extremity Symmetry Index (LSI)
A. Distance Measures: LSI = involved side/uninvolved side x 100%
B. Time Measures: LSI = uninvolved side/involved side x 100%

Hop testing incorporates sport specific requirements including directional changes, speed, lower limb confidence, strength/control and acceleration and deceleration (4). Despite the functional and demanding nature of hop testing, there is very little research on the predicative value of these tests on injury after returning to sports, none found during the research period of this article. There is however, a test that does have support for its predictive value for injury after returning to sport after lower extremity injury. This test is the Star Excursion Balance Test (5,6). A panel at Cincinnati Children’s Hospital Medical Center recommended to add the Star Excursion Balance Test to a functional test battery for return to sport following lower extremity injury. The original study reported that those with composite reach distance scores of less than 94% of their limb length were significantly more likely to sustain a lower extremity injury during the athletic season (6). The Star Excursion Balance Test had participants stand on 1 leg and reach with opposite limb in 3 directions including, anterior, posteromedial, and posterolateral. Composite scores summed the reaches in all the directions and divided by the patient’s leg length (6).

Calculating the Star Excursion Balance Test (SEBT)
SEBT = ((Ant. Distance + Post. Lat. Distance + Post. Med. Distance)/Leg Length of Stance Limb) x 100%

In conclusion, the use of a battery of functional tests following ACL repair would be best to determine readiness to return to sport and reduce risk of injury upon return to sport. Research supports the use of the Lower Limb Symmetry Index (4 part hop test), and the Star Excursion Balance Test because they are practical, valid, reliable and mimic the requirements of sports. Requirements for these tests, for return to sport, include 85% or more on the LSI, and at least 94% of limb length on the SEBT (2,4,5,6). Patients following this surgical repair must also meet the other requirements of their protocol, likely including full range of motion, resolution of pain and 90% strength of their uninjured limb for safest return to sport. Physician clearance is also recommended. So, when your next patient following ACL repair asks you when they will return to sport, tell them, “When you can demonstrate you are ready.”


Last revised: September 11, 20111
by Amber Wacek, DPT

1. Kvist, J. Rehabilitation following anterior cruciate ligament injury. Sport Med. 2004;34(4):269-280.
2. Noyes, F.R. et al. Abnormal lower limb symmetry determined by functional hop test after anterior cruciate ligament rupture. Am J Sport Med. 2004;19(5):513-518.
3. Ross, M.D., Lanford, B., & Whelan, P. Test-retest reliability of 4 single-leg horizontal hop tests. Journal of Strength & Conditioning. 2002;16(4): 617-622.
4. Reid, A., Birmingham, T.B., Stratford, P.W., Alcock, G.K., & Giffin, J.R. Hop Testing provides a reliable and valid outcome measure during rehabilitation after anterior cruciate ligament reconstruction. Physical Therapy. 2007;87(3):337-349.
5. Cincinnati Children’s Hospital Medical Center Return to Activity Evidence-Based Practice Team 2009. Evidence Based Care Guideline for Return to Activity after Lower Extremity Injury. (2010) p. 1-13. Guideline 38.
6. Plisky, P.J., Rauth, M.J., Kaminski, T.W., & Underwood, F.B. Star Excursion Balance Test as a predictor of lower extremity injury in high school basketball players. J Orthop Sports Phys Ther. 2006;36(12): 911-919. 

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