Concentric and eccentric torque variations of the quadriceps femoris in patellofemoral pain syndrome.

The purpose of this study was to investigate the extent of torque reduction in the quadriceps femoris in subjects complaining of patellofemoral pain syndrome compared to subjects with sound knees. Fifty-five patients (21 women and 34 men) and 30 healthy subjects (15 women and 15 men) took part in this study. Using the KINCOM isokinetic dynamometer, quadriceps torque was assessed at 30°/s, 60°/s, and 120°/s, both in the concentric and eccentric modes. Findings demonstrated a significant (P < 0·01) reduction of between 30% and 40% in the patients when compared with the control group. This reduction was not speed or mode-specific. Men were stronger than women by a margin of 22% and 14% for the concentric and eccentric modes in the control group. Parallel figures for the patellofemoral pain syndrome group were 25% and 17%. Good to high correlations were found between peak and average torque in both groups. There were no significant differences between the muscles referring to the dominant versus the non-dominant legs of the control group.