Tibio-femoral Kinematics of Soft and Stiff Landings: A Biplane Fluoroscopy Study

INTRODUCTION: Though the exact mechanism of non contact anterior cruciate ligament (ACL) has not been fully clarified, several recent studies have suggested individuals who land with a stiff landing profile, defined as reduced knee flexion angles, may be at higher risk of ACL injury than individuals who land more soft [1,2]. The concepts and theories developed from these and other non-contact ACL injury studies have contributed to the development of performance based ACL injury prevention training programs [3,4]. A major component of these programs is neuromuscular training, in which individuals are trained to land with increased knee flexion angles. Though these programs have been shown to be effective in reducing the incidence of ACL injury of female athletes, the specific mechanisms by which injury risk is reduced has not been determined. The purpose of the current study is to measure tibio-femoral kinematics of the knee during soft and stiff landings. We hypothesize that stiff landings will exhibit larger anterior tibial translation (ATT), internal rotation, and valgus angle, thus placing individuals at higher risk of ACL injury.