Shoe-surface friction influences movement strategies during a sidestep cutting task: implications for anterior cruciate ligament injury risk.

BACKGROUND Increasing the coefficient of friction of the shoe-surface interaction has been shown to lead to increased incidence of anterior cruciate ligament (ACL) injuries, but the causes for this increase are unknown. Previous studies indicate that specific biomechanical measures during landing are associated with an increased risk for ACL injury. HYPOTHESIS At foot contact during a sidestep cutting task, subjects use different movement strategies for shoe-surface conditions with a high coefficient of friction (COF) relative to a low friction condition. Specifically, the study tested for significant differences in knee kinematics, external knee moments, and the position of the center of mass for different COFs. STUDY DESIGN Controlled laboratory study. METHODS Twenty-two healthy subjects (11 male) were evaluated performing a 30 degrees sidestep cutting task on a low friction surface (0.38) and a high friction surface (0.87) at a constant speed. An 8-camera markerless motion capture system combined with 2 force plates was used to measure full-body kinematics, kinetics, and center of mass. RESULTS At foot contact, subjects had a lower knee flexion angle (P = .01), lower external knee flexion moment (P < .001), higher external knee valgus moment (P < .001), and greater medial distance of the center of mass from the support limb (P < .001) on the high friction surface relative to the low friction surface. CONCLUSION The high COF shoe-surface condition was associated with biomechanical conditions that can increase the risk of ACL injury. The higher incidence of ACL injury observed on high friction surfaces could be a result of these biomechanical changes. The differences in the biomechanical variables were the result of an anticipated stimulus due to different surface friction, with other conditions remaining constant. CLINICAL RELEVANCE The risk analysis of ACL injury should consider the biomechanical movement changes that occur for a shoe-surface condition with high friction.