EFFECT OF QUADRICEP STRENGTH SYMMETRY ON KNEE JOINT SYMMETRY DURING SLS IN ACLR AND HEALTHY INDIVIDUALS
A tear of the anterior cruciate ligament (ACL) is one of the most common and costly injuries for active adults and athletes. This injury causes short- and long-term problems economically through increased health care costs and physically through delayed playing time and early-onset knee osteoarthritis (OA). Athletes returning to high level sports after ACL reconstruction are over four times more likely to reinjure the reconstructed ACL(ACLR) than athletes at lower levels. Risk factors for reinjury are an area of interest for researchers in order to minimize this short-term burden. The high rates of a second ACL tear suggest current inadequate return-to-play (RTP) criteria which focuses on establishing symmetry between the injured and uninjured limb mainly through clinical hop tests and self-reported function surveys such as the KOOS and IKDC. However, to date, the only significant risk factors for a second ACL injury are time after an ACLR and quadricep strength symmetry. Quadricep strength symmetry is most commonly assessed using a dynamometer. However, these devices are not typically found in clinical settings. Thus, a clinically applicable movement that could ultimately be added to the RTP criteria to assess quadricep strength asymmetry is the single leg squat (SLS). PURPOSE: The purpose of this study was to determine the effect of quadriceps strength LSI on knee joint biomechanics LSI during a single leg squat in ACLR and healthy individuals. METHODS: A two cohort (ACLR and healthy) within-groups study design was used to assess the purpose of this study. ACLR individuals (n=10) filled out the KOOS self-report survey. Both healthy (n=10) and ACLR underwent the single leg hop for distance, triple leg hop for distance, and 6m timed hop on both limbs. All participants were then strength assessed on the quadriceps for both limbs using a dynamometer; isometrically at 60 degrees. Lastly, using a 10-camera motion capture system, participants completed 5 SLS per limb as well as a landing task from 75% their maximal hop distance. RESULTS: ACLR participants were split into two groups: those with >90% quadricep strength symmetry and those with <90% quadricep strength symmetry. All groups achieved an average hop distance LSI of greater than 90%. There was no effect within group or between group for any of the biomechanical measurements (peak knee flexion angle, peak knee extensor torque, total knee mechanical work) during the SLS. There were not any strong correlations between quadricep strength LSI and peak knee extensor torque or total mechanical work during the SLS. CONCLUSION: The SLS functional task was not sensitive enough to detect isometric quadricep strength deficiencies. Individuals in all groups appeared to move similarly through the SLS, both through the biomechanical LSIs but also joint contributions of the hip, knee, and ankle. The only distinction that the <90% ACLR group had from the other two groups was their peak knee extensor torques normalized to body mass during the isometric contractions. They displayed a 2.0 Nm/kg normalized torque for both limbs, while both the >90% ACLR and healthy controls displayed a 3.0 Nm/kg normalized torque for both limbs. This overall suggested that future studies should look at both limbs reaching functionality and strength before RTP, with functionality being defined by absolute values, not the contralateral limb in comparison to the ipsilateral limb.
Wilhelm, Claire. (May 2022). EFFECT OF QUADRICEP STRENGTH SYMMETRY ON KNEE JOINT SYMMETRY DURING SLS IN ACLR AND HEALTHY INDIVIDUALS (Master's Thesis, East Carolina University). Retrieved from the Scholarship. (http://hdl.handle.net/10342/10665.)
Wilhelm, Claire. EFFECT OF QUADRICEP STRENGTH SYMMETRY ON KNEE JOINT SYMMETRY DURING SLS IN ACLR AND HEALTHY INDIVIDUALS. Master's Thesis. East Carolina University, May 2022. The Scholarship. http://hdl.handle.net/10342/10665. December 08, 2023.
Wilhelm, Claire, “EFFECT OF QUADRICEP STRENGTH SYMMETRY ON KNEE JOINT SYMMETRY DURING SLS IN ACLR AND HEALTHY INDIVIDUALS” (Master's Thesis., East Carolina University, May 2022).
Wilhelm, Claire. EFFECT OF QUADRICEP STRENGTH SYMMETRY ON KNEE JOINT SYMMETRY DURING SLS IN ACLR AND HEALTHY INDIVIDUALS [Master's Thesis]. Greenville, NC: East Carolina University; May 2022.
East Carolina University