RELATIONSHIP BETWEEN HIP MUSCLE STRENGTH AND KINEMATICS OF THE KNEE JOINT OBJECTIVES: Patellofemoral pain syndrom is a common problem experienced by active adults and adolescents. Ascending stairs is one of the most painful activities of daily living in person with patellofermoral pain syndrome. However, its etiology has remained vague and is controversial. Nevertheless previous studies were reported from either the viewpoint of kinematics of the knee joint or hip muscle weakness, and is unclear whether hip and knee muscle weakness affect on knee medial displacement during physical acitvities.   of the this study was to determine relationship between hip muscle strength and kinematics of the knee joint. METHODS:  Forty healthy subjects participated in this study. The knee medial displacement was measured during a functional tests using two high speed cameras. Images of videos were processed using motion analysis software. 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. Hip and knee muscle strengths were measured using a hand held dynamometer as isometric muscle strength referring to Katoh’s method. RESULTS: Muscle strength of hip external rotators was associated with knee medial displacement during both single leg squatting (r= - 0.519, P< 0.001) and dropping (r= -0.520, P< 0.001). CONCLUSIONS: The present results suggest that hip muscles’ strength, particularly hip external rotators’ strength are closely associated with knee medial displacement.