Purpose: Genu varum deformity changes the line of gravity from center of knee towards the medial side. This deviation results in changes in the upper part of the lower extremity that can affect postural control as well as the position and activity of the proximal muscles of the knee joint, like the gluteus medius muscle. Therefore this study aims to investigate the effect of genu varum disorder on the activity of gluteus medius muscle and postural control during single-leg jump-landing exercise.
Methods: A total of 28 male students of Physical Education Major (Mean [SD] age, weight, and height: 21.53[1.65] y, 66.76[7.51] kg, and 173.38[4.54] cm, respectively) were enrolled and studied in two groups of genu varum (14 students) and normal ones (14 students). The activity level of gluteus medius muscle and the ground reaction force were measured using electromyography device and force plate, respectively in single-leg jump-landing exercise. In order to analyze the data, we used the Independent t test at significance level of P<0.05. Participants were asked to perform the single-leg jump-landing exercise with 50% of maximum vertical jump and land on the force plate using one leg. The RMS of gluteus medius muscle was measured using MATLAB software.
Results: There is a significant difference between the genu varum and normal group in terms of mean activity of gluteus medius muscle before and after the landing. There were significant difference between these groups with regard to time to stabilization in anterior-posterior direction, while significantly higher time to stabilization was found in the genu varum group compared to the normal groups in medial-lateral and overall direction. The time to stabilization of the subjects in the directions of medial-laterallateral and anterior-posterior and total Resultant Vector (RV) using the force plate in the jump-landing movement was evaluated. There was no significant difference in the time to stabilization between the two groups of the knee parenthesis and the normal knee in the anterior-posterior direction (P>0.05), but the time to stabilization in the medial-lateral and in resultant vector direction in the genu varum group was significantly more than those in normal knee group (P<0.05).
Conclusion: Participants with genu varum have weakness in postural stability in medial-lateral and total RV direction that might decrease the activity of gluteus medius muscle. This might increase the demand on the muscle for stabilizing hip and pelvis which decreases control of transverse and frontal part of hip and finally affects postural stability in medial-lateral direction (may be due to inappropriate activity of the hip). Thus, improvement of gluteus medius muscle might improve medial-lateral control of the posture in individuals with genu varum.