Single Leg Squat Test and Its Relationship to Dynamic Knee Valgus and Injury Risk Screening

Abstract Background Lower extremity injuries are common in athletes. Valid tests to assess for risk of injury that are easily performed during a preparticipation sports physical examination are lacking. Two-dimensional (2D) analysis of the drop-jump test can identify athletes at risk, but it is too expensive and cumbersome to use in this setting. Objective To identify if those who perform a “positive”(abnormal postures) single leg squat (SLS) test also exhibit greater “dynamic valgus” on the 2D drop-jump test. Our secondary purpose was to assess whether group differences in gender, age, or body mass index are evident between those who exhibit a positive SLS test result versus a negative SLS test result. Also, we wanted to determine any gender differences with the 2D drop-jump test. Design A cross-sectional study. Setting Private practice, preparticipation sports physical examinations. Participants A total of 142 middle school and high school athletes. Methods Participants performed a SLS test and a drop-jump test during their preparticipation sports physical examination. Individuals were partitioned into groups based on the outcome of their SLS test (positive SLS group versus negative SLS group). Independent sample t -tests were used to evaluate SLS group differences in the drop-jump test, age, and body mass index, and the χ2 test was used to evaluate SLS group differences in gender ( P ≤ .05). Main Outcome Measurements The SLS test and drop-jump test. Results Seventy-three of the 142 athletes (51%) had a positive SLS test result, whereas 69 athletes (49%) had a negative SLS test result. Individuals in the positive SLS group had a significantly lower knee-hip ratio), indicative of greater dynamic knee valgus, than did those in the negative SLS group ( P = .02). Individual characteristics between SLS groups including gender, age, and body mass index were similar. Conclusion The SLS test is a reasonable tool to use in preparticipation sports physical examinations to assess for dynamic knee valgus and the potential risk of lower extremity injury.