ABSTRACT
The lower extremity deformities have been co nsidered to change the relations between body segments. Postural stability could be affected by these changes in the alignment and positioning of the body segments. The purpose of this study was to examine postural response and surface electromyographic activity of selected lower limb muscles to recover upright posture following a sudden external perturbation among individuals with genu valgum in comparison with age matched healthy controls. In this case-control study, sixteen subjects with genu valgum and sixteen agematched healthy controls were participated. With unexpected perturbation, the displacement of the center of pressure [COP] and surface electromyographic activity of selected lower limb muscles were collected. Data were analyzed using independent t-test [P<0.05]. The genu valgum group had a greater COP displacement after perturbation in comparison with the control group [P<0.05]. Activities of some of the lower limbs muscles were significantly higher in genu valgum group in comparison with controls group after perturbation in different directions. These findings illustrate that abnormal lower limb alignment as risk factor can decrease postural reaction strategy in response to a sudden balance perturbation. Designing a strength training program for vastus medialis muscle may have beneficial effects in the prevention of knee injuries in individuals with knee valgus deformity