The effects of quadriceps strengthening on pain, function, and patellofemoral joint contact area in persons with patellofemoral pain.

OBJECTIVE: Patellar malalignment is a major cause of patellofemoral pain syndrome (PFPS), but the relationship between clinical symptoms and changes in patellar position and knee muscle strength has not been confirmed. This study examined the effect of weight training on hip and knee muscle strength, patellofemoral joint contact area, and patellar tilt on subjects with and without PFPS, hoping to develop an optimal rehabilitation protocol for subjects with PFPS.
DESIGN: The study uses a prospective independent group comparison. Fifteen subjects with and without PFPS were assessed for knee strength, patellofemoral joint contact area, and patellar tilt angle using magnetic resonance imaging. The subjects with PFPS were also examined and given a numeric pain rating score and a Kujala patellofemoral score. The subjects performed lower-limb weight training 3 times/wk for 8 wks, and the outcomes were assessed both before and after training.
RESULTS: Subjects with PFPS have increased their patellofemoral joint contact area after weight training (P < 0.001). No statistical significant change was found on the patellar tilt angle. The isometric and isokinetic knee strength in subjects with and without PFPS have increased after weight training (P value increased from 0.007 to 0.05). Both numeric pain rating and Kujala patellofemoral score in the PFPS group improved after training (P < 0.001).
CONCLUSIONS: Weight-training exercise increased knee muscle strength and the patellofemoral joint contact area, which could reduce mechanical stress in the joint, improving pain and function in subjects with PFPS.