Postural stability and isokinetic strength do not predict knee valgus angle during single-leg drop-landing or single-leg squat in elite male rugby union players

BACKGROUND: Knee injuries have been identified as the most common injury in rugby. Knee valgus has been identified as a risk factor for ligament injuries in athletes and predictors of knee valgus may assist in the design of knee injury prevention programs. PURPOSE: The purposes of this study were to use postural stability (PS) and strength measures to predict knee valgus angle during dynamic tasks, identify relationships between PS and strength, and compare measures between positions. METHODS: Participants presenting positive during a gluteal dysfunction screening exam were enrolled. Participants performed PS, isokinetic strength, and biomechanical assessments. Stepwise multiple linear regression analyses were performed to identify predictors of knee valgus. Correlation coefficients identified relationships between PS and strength, and independent t-tests compared forwards and backs. RESULTS: Backs had significantly (p< 0.05) better PS and greater strength as compared to forwards. Hip abduction strength was correlated (r=- 0.52 - 0.71, p< 0.05) with all eyes open static PS measures. Regression analysis failed to identify predictors of knee valgus angle. CONCLUSION: Although PS and strength were not multivariate predictors of knee valgus in male rugby players, bivariate correlations suggest that hip abduction strength training may be beneficial for enhancing PS.