The effects of hip musculature on knee valgus during a squat task with and without a 2-inch heel block

Objective: To compare hip ROM, strength, muscle activity, and ankle dorsiflexion ROM between groups that demonstrate knee valgus during a squat task and those that do not (control). Also, determine if muscle activity changes after knee valgus is corrected by a twoinch heel block. Design: A single-session experimental research design was used to compare the control group and the valgus group. Participants: Seventeen (10 Females, 7 Males) control subjects (age[yr] = 23.82 ± 5.76, height[cm] = 166.12 ± 31.13, weight[kg] = 69.59 ± 15.37) and fourteen (12 Female, 2 Male) valgus subjects (age[yr] = 22.36 ± 3.08, height[cm] = 167.21 ± 9.3, weight[kg] = 65.93 ± 9.9) without lower extremity injury. Dependent Variables: Supine hip abduction and external rotation ROM. Ankle dorsiflexion ROM (straight and bent knee). Hip internal rotation, external rotation, extension, and abduction eccentric and concentric peak torque and time to peak torque. EMG mean amplitude of the gluteus maximus, gluteus medius and adductor complex during a squat with and without a two inch heel block. Data Analysis: Mixed model analysis of variance tested for difference both between and within groups. Results: A significant group by phase interaction effect (p = 0.02) existed for mean adductor amplitude between the valgus and the control group. A significant difference (p < .001) in straight knee ankle dorsiflexion ROM existed between the control and the valgus group. A significant difference (p = 0.034) existed between the internal rotation concentric time to peak torque between the two groups. Conclusion: The adductor complex plays a significant role in hip extension. Increased activity of the adductor during extension could pull the knees into valgus. Gastrocnemius tightness might contribute to knee valgus during a squat. There appears to be three distinct populations when considering this knee valgus squatting position. 1. Normal individuals who do not have valgus. 2. Ankle dysfunction individuals who’s valgus position corrects with a heel block. 3. Hip dysfunction individuals who’s valgus position does not correct with a heel block