Relationship of hip and ankle range of motion, trunk muscle endurance with knee valgus and dynamic balance in males.

OBJECTIVES: Investigate the relationship of hip internal rotation (IR) and ankle dorsiflexion (DF) range of motion (ROM), trunk flexor, extensor, and lateral flexor muscle endurance with frontal plane knee projection angle (FPKPA) and Y-balance test (YBT).

STUDY DESIGN: Cross-sectional study.

SETTING: Armed Force training site.

PARTICIPANTS: 121 healthy male militaries with no history of musculoskeletal injury in the last 6 months.

MAIN OUTCOMES: FPKPA was evaluated during single-leg squat. YBT was assessed on the anterior, posterolateral and posteromedial directions. Passive hip IR ROM and weight-bearing ankle DF ROM were measured with a digital inclinometer. Trunk muscle endurance was measured as the time the participant could hold the positions.

RESULTS: FPKPA was predicted by ankle DF ROM and hip IR ROM (r2  = 0.340; P = 0.009). For YBT anterior, ankle DF ROM was the only predictor (r2  = 0.32; P < 0.001); whereas trunk extensor endurance predicted YBT posterolateral (r2  = 0.273; P < 0.001) and YBT posteromedial (r2  = 0.033; P = 0.045).

CONCLUSION: The results suggest that increasing hip stiffness and ankle mobility might help to control dynamic knee alignment. In addition, the dynamic balance could be improved increasing ankle DF ROM and trunk extensor endurance.