A Comparison of EMG Activity of Some Lower Extremity Muscles in Individuals with and without Dynamic Knee Malalignment in Single-Leg Squat

Correct kinematics is an effective factor to reduce musculoskeletal problems. The aim of this study was to compare muscle activity during single-leg squat (SLS) in a group with dynamic knee malalignment (DKMG) and normal cases. 23 active females (mean age of 21.86±2) participated in this comparative study. Lower limb Muscle activity (RMS), pelvic drop angle (PDA), trunk side bend (TSB) and knee valgus (KV) was recorded during SLS. Independent t test was used to compare variables and significance level was 0.05. The results showed no significant differences in PD (P=0.86) and TSB (P=0.25), but KV was greater in DKMG than the control group (P=0.00). Although %MVC of all muscles was greater in DKMG than the control group, only rectus femoris (P=0.04) and gluteus maximus (P=0.05) showed significant differences. Also, a weak correlation between KV with TSB (r=0.33) and rectus femoris activity (r= -0.37) was observed. Findings showed that DKMG had more muscle activity especially in rectus femoris and gluteus maximus which showed the important role of these muscles in controlling lower limb alignment during functional movements. Also, dynamic knee malalignment may deviate trunk towards weight bearing leg for substitution during SLS.