QUADRICEPS FEMORIS ACTIVATION CHANGES IN GENU VARUM - A POSSIBLE BIOMECHANICAL FACTOR IN THE PATHOGENESIS OF OSTEOARTHROSIS

This study was designed to determine whether the presence of an alignm ent deformity of the lower leg, known as genu varum, causes abnormalit ies in individual- or group-activation of the surrounding knee extenso rs, a situation which might accelerate knee deterioration. Nine health y women with normal tibial alignment were compared with nine age-match ed healthy women with genu varum. The outcome measure of maximal quadr iceps femoris activity was recorded during successive maximal concentr ic isometric and isokinetic contractions of the knee extensors perform ed on a dynamometer using surface electromyography. The results showed that, taken as a whole, the percentage utilization of quadriceps moto r units was higher for those subjects with genu varum (p < 0.01). Thes e findings demonstrate that the extensors surrounding a varus knee mig ht function less efficiently than those surrounding a normally aligned knee. As such they suggest that pathological force generation across a varus knee might be caused, in part, by associated alterations in qu adriceps tension generating capacity.