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.