Relationship Between Hip Muscle Strength and Kinematics of the Knee Joint during Single Leg Squatting and Dropping

Abstract

[Purpose] The aim of this study was to determine relationship between hip muscle strength and kinematics of the knee joint during single leg squatting and dropping. [Subjects] Twelve healthy subjects participated in this study. [Methods] The knee medial displacement was measured during single leg squatting and dropping using a high-speed camera. Peak isometric muscle strengths of the following muscles were measured hip abductors, hip adductors, hip external rotators, hip internal rotators, knee extensors and knee flexors. [Results] Muscle strength of hip external rotators was associated with knee medial displacement during both single leg squatting (r=-0.69) and dropping (r=-0.59), and muscle strength of knee flexors was associated with knee medial displacement during dropping (r=-0.58). [Conclusion] The present results suggest that hip muscles' strength, particularly hip external rotators' strength are closely associated with knee medial displacement.