Women with patellofemoral pain syndrome have quadriceps femoris volume and strength deficiency.

Purpose: the aim of this study was to assess muscle torque, total volume, and cross-sectional area, and lower limb function of the quadriceps muscle in women with unilateral patellofemoral pain syndrome (PFPS).

Methods: twenty-four women with unilateral patellofemoral pain participated in the study, with each subject acting as their own internal control by using the unaffected limb. quadriceps muscle torque was measured with the Isomed 2000. The total volume and cross-sectional area (CSA) of the quadriceps muscle were measured by using magnetic resonance imaging. Lower limb function was assessed by hop and step-down tests.

Results: there was a significant difference in the total volume (P < 0.05) and in the cross-sectional area (P < 0.05) of the quadriceps muscle between affected and unaffected sides. There was a significant difference in the peak torque of the quadriceps muscle at 60°/s between affected and unaffected sides (P < 0.05). There were significant correlations between quadriceps largest CSA and volume on the affected side (P < 0.05) and on the unaffected side (P < 0.05). There were significant negative correlations between the smallest CSA and the peak torque at 180°/s (P < 0.05) and at 60°/s (P < 0.05) on the affected side.

Conclusions: decreased torque, total volume, and CSA of the quadriceps muscle are presented in unilateral with PFPS although cause or effect cannot be established. Large prospective longitudinal studies are needed to detect the changes in the muscle structure and to establish whether these features are a cause of PFPS.