Single-leg Squat

Abstract

The Single Leg Squat (SLS) is a commonly performed clinical screening tool used to identify faulty lower extremity biomechanics, specifically dynamic knee valgus. Despite this use, few studies have investigated its reliability or examined if sex-differences exist in SLS performance in athletic populations. PURPOSE: Determine interrater reliability of the SLS and investigate whether occurrence of medial knee displacement (MKD) differed between male and female collegiate athletes. METHODS: Ninety-two injury-free Division I collegiate athletes completed SLS testing as part of their preparticipation exam, including 46 men (age=18.6±1.6y, height=183.5±7.9 cm, mass=91.0±18.9 kg) and 46 women (age=18.6±1.6y, height=169.1±9.5 cm, mass=65.4±10.4 kg). Participants completed 5 consecutive SLSs on each leg while being recorded with a standard video camera from the frontal plane view. Videos were slowed and paused for scoring purposes. Participants were assigned a positive (+) SLS score if the midpoint of the patella moved to the great toe during the SLS in at least 3 of the 5 trials. Trials were scored by 2 members of the research team (GM, RM). Frequency counts were calculated and agreement of the SLS was analyzed with an unweighted kappa statistic for a subset of 50 participants. Pearson Chi-square tests were used to evaluate the association between sex and SLS performance. RESULTS: The interrater reliability for the right and left-leg SLS scores was 0.762 and 0.634, respectively, which indicated a substantial level of agreement. The overall percent agreement was 85%. More than half (50 of 92; 54.3%) of all athletes had a (+) SLS test result in at least 1 leg; 29.3% (27 of 92) had a (+) SLS in both legs. No association was found between sex and a (+) SLS score in at least 1 leg (χ2=0.175; p=0.675, OR=1.19, 95%CI=0.52-2.71). Although not significant, females were roughly twice as likely (χ2=2.57; p=0.109, OR=2.11, 95%CI=0.84-5.30) to have a (+) SLS score on both legs in comparison to males. CONCLUSION: The interrater reliability for the MKD component of the SLS demonstrated a substantial level of agreement. Although not significant, female collegiate athletes displayed a greater occurrence of bilateral MKD than male collegiate athletes. Future work will determine if SLS performance is a predictor of injury in collegiate athletes.