Sagittal plane body kinematics and kinetics during single-leg landing from increasing vertical heights and horizontal distances: Implications for risk of non-contact ACL injury

Purpose: This study identified kinematic and knee energetic variables that reduce the risk of non-contact anterior cruciate ligament (ACL) injury during single-leg landings from increasing vertical heights and horizontal distances. Methods: Nine subjects performed single-leg landings from takeoff platforms with vertical heights of 20, 40, and 60 cm onto a force plate. Subjects also performed single-leg landings from a 40 cm high takeoff platform placed at horizontal distances of 30, 50 and 70 cm from a force plate. Kinematic and kinetic data were measured. Results: Vertical height had a significant and positive effect on peak vertical ground reaction force (VGRF) (p<0.001), peak posterior ground reaction force (PGRF) (p=0.004), knee flexion angle (p=0.0043), trunk flexion angle (p=0.03), knee power (p<0.001) and knee work (p<0.001). There was also a significant and positive effect of horizontal distance on peak PGRF (p<0.001), ankle plantar flexion angle (p=0.008), hip flexion angle (p=0.007), and trunk flexion angle (p=0.001). At increasing vertical height, peak VGRF was significantly correlated to ankle plantar flexion and knee flexion angles (r=-0.77, p=0.02 and r=-0.78, p=0.01, respectively). At increasing horizontal distance, peak PGRF was significantly correlated to ankle plantar flexion angle, knee power and knee work (r=0.85, p=0.003; r=0.67, p=0.04; and r=0.73, p=0.02, respectively). Clinical Relevance: A better understanding of the risk factors to non-contact ACL injury during single-leg landings from increasing vertical heights and horizontal distances can aid in the design of injury prevention regimen. (C) 2012 Elsevier B.V. All rights reserved.