Association between Femoral Anteversion and Lower Extremity Posture upon Single-leg Landing: Implications for Anterior Cruciate Ligament Injury.

[Purpose] Increased femoral anteversion may occur with hip internal rotation and valgus knee alignment upon landing and is considered a risk factor for anterior cruciate ligament injury. We examined the relationship between femoral anteversion and joint motion and muscle activity of the lower extremity in terms of the risk factors for anterior cruciate ligament injury. [Subjects] Sixteen healthy females were divided on the basis of femoral anteversion into low and high groups. [Methods] Femoral anteversion was assessed using Craig's test. We performed kinematic analysis and measured the electromyography activity of the lower extremity upon left single-leg landing. [Results] The high group had a significantly lower hip flexion angle and higher knee flexion and valgus angles than the low group. The rectus femoris showed significantly greater electromyography activities in the high group than in the low group. [Conclusion] These results suggest that increased femoral anteversion results in lower hip flexion angle, higher knee valgus alignment, and greater rectus femoris muscle activity, leading to anterior tibial displacement upon single-leg landing. Increased femoral anteversion may be a potential risk factor for anterior cruciate ligament injury.