The Relationship between Hip Strength and Peak Knee Valgus Angle during Single Leg Squat

Abstract

Objectives: Available research is limited and conflicting with regard to the role of the hipmuscles in controlling knee valgus. Thus, the aim of this study is to investigatewhether hip muscle's strength is significantly related to peak knee valgus angle (PKVA)during a single leg squat. Methods: A correlation research design was chosen to test the hypotheses of this study in 30 healthy subjects (17 males and 13 females). Procedures included isometricstrength testing using the DILLON ED junior dynamometer for hip (abduction/adduction,flexion/extension, and internal/external rotation). Subjectswere videotaped as they performed single leg squats using two digital video cameras.Video data for squat trials were analyzed using the siliconCOACH Pro Version 6. Results: ICC values indicated excellent reliability for PKVA(0.948). Pearson correlation coefficients demonstratedsignificant negative relationships between hip abduction (r =-0.550), adduction (r =-0.475), extension (r =-0.421), and PKVA. Linear regression analysis revealed that hip extensors, abductors and adductorsaccounted for 17.7%, 30.3% and 26.6% respectively, of variance in PKVA Conclusions: SiliconCOACH by one rater produced a reliable measurement of knee angle in frontal plane during single leg squat in healthy population. Decreased isometric strength of hip abductors, adductors and extensors was closely associated with increased peak valgus angle at the knee. This relationship is of clinical relevance when designing rehabilitative and injury prevention strengthening programs.