Biomechanical risk factors of non-contact ACL injuries: A stochastic biomechanical modeling study

BackgroundSignificant efforts have been made to identify modifiable risk factors of non-contact anterior cruciate ligament (ACL) injuries in male and female athletes. However, current literature on the risk factors for ACL injury are purely descriptive. An understanding of biomechanical relationship between risk and risk factors of the non-contact ACL injury is necessary to develop effective prevention programs.PurposeTo compare lower extremity kinematics and kinetics between trials with and without non-contact ACL injuries and to determine if any difference exists between male and female trials with non-contact ACL injuries regarding the lower extremity motion patterns.MethodsIn this computer simulation study, a stochastic biomechanical model was used to estimate the ACL loading at the time of peak posterior ground reaction force (GRF) during landing of the stop-jump task. Monte Carlo simulations were performed to simulate the ACL injuries with repeated random samples of independent variables. The distributions of independent variables were determined from in vivo laboratory data of 40 male and 40 female recreational athletes.ResultsIn the simulated injured trials, both male and female athletes had significantly smaller knee flexion angles, greater normalized peak posterior and vertical GRF, greater knee valgus moment, greater patella tendon force, greater quadriceps force, greater knee extension moment, and greater proximal tibia anterior shear force in comparison to the simulated uninjured trials. No significant difference was found between genders in any of the selected biomechanical variables in the trials with simulated non-contact ACL injuries.ConclusionSmall knee flexion angle, large posterior GRF, and large knee valgus moment are risk factors of non-contact ACL injury determined by a stochastic biomechanical model with a cause-and-effect relationship.