Altered hip and trunk muscle function in individuals with patellofemoral pain.

OBJECTIVE The purpose of this study was to investigate the role of hip muscles in patellofemoral pain (PFP), specifically by investigating neuromotor control, strength and range of motion of the hip muscles. DESIGN Cross-sectional. SETTING University laboratory. PATIENTS Ten participants diagnosed with PFP and 27 asymptomatic controls were recruited, using standard inclusion and exclusion criteria. MAIN OUTCOME MEASURES Electromyographic activity of the vasti and anterior gluteus medius (GM) were recorded using surface electrodes and posterior GM using fine wire electrodes while the participant completed a stair-stepping task. Hip strength and trunk side flexion strength was assessed using a hand-held dynamometer and hip range of motion with an inclinometer. Pain and disability measures were recorded for the PFP participants. RESULTS When individuals with PFP completed the stair-stepping task there was a delay in activation of both anterior and posterior GM (p<0.02) and an alteration in vasti control (p = 0.001). In addition, trunk side flexion strength was significantly less (29%) in individuals with PFP (p = 0.03). CONCLUSION This study provides evidence that trunk side flexion strength and neuromotor control of the GM are affected in people with PFP. This study also confirms the presence of a delayed vastus medialis obliquus relative to vastus lateralis, providing further evidence underpinning the importance of retraining the vasti function in patients with PFP.