Lower extremity strength and mechanics during jumping in women with patellofemoral pain.

CONTEXT Lower extremity (LE) weakness might be associated with altered mechanics during weight bearing in subjects with patellofemoral pain syndrome (PFPS). OBJECTIVE To analyze LE strength, mechanics, and the association between these variables among women with and without PFPS during a simulated athletic task. DESIGN Case control. SETTING Motion-analysis laboratory. SUBJECTS 20 women with PFPS and 20 healthy women. MAIN OUTCOME MEASURES Peak isometric lateral trunk-flexion, hip-abduction, hip external-rotation, knee-flexion, and knee-extension strength, as well as hip- and knee-joint excursions and angular impulses during single-leg jumps. RESULTS PFPS subjects produced less hip-abduction, hip external-rotation, and trunk lateral-flexion force than the control group. The PFPS group also demonstrated greater hip-adduction excursion and hip-abduction impulses. The association between the strength measurements and LE mechanics was low. CONCLUSIONS Women with PFPS demonstrate specific weaknesses and altered LE mechanics. Weakness is not, however, highly correlated with observed differences in mechanics.