Changes in lower limb orientation with four different drop–landing directions

Abstract

One of the representative injury mechanisms of anterior cruciate ligament (ACL) injuries and tears, which are serious sports injuries, involve knee valgus that occurs during landing from jumping and side cutting movement. This study aimed to investigate the risk factor of ACL injury or rupture by using the multi-directional landing motion, which is believed to induce the injury or rupture. We captured 3D joint displacement using four high–speed cameras and calculated joint angle in the lower extremity and torso from initial ground contact (touchdown) to the time of peak vertical ground reaction force found. While there were no differences in the knee valgus displacement after landing regardless of differences in landing direction, there was a strong positive correlation between the knee valgus and the external rotation of the knee in all landing directions, both for the dominant and non-dominant leg. This suggests that as external rotation of the knee increased, knee valgus increased. We also found that, at touchdown, a positive correlation between knee valgus and hip flexion (0° direction), and also between knee flexion (30°, 60°, 90° directions) in the dominant foot, and a positive correlation between knee valgus and hip external rotation (0°, 30°, 60°, 90° directions) in the non-dominant foot. The results suggest that increases in the knee valgus was due to the increases in the knee flexion in the dominant foot, and the increases in the hip external rotation in the non-dominant foot at touchdown.