Biomechanics of prophylactic knee bracing for preventing knee injury during landing

© 2015 Dr. Katie Ang-Mei EwingProphylactic knee braces are designed to prevent knee injuries during athletic activities, including anterior cruciate ligament (ACL) rupture, which results in painful, costly, and long-term consequences. Non-contact ACL injuries commonly occur during high-risk maneuvers, such as rapid changing of direction or landing from a jump, and have rapidly increased over the past decade. However, previous studies have provided conflicting results on the use of prophylactic knee braces for preventing knee injuries. The overall objective of this dissertation was to provide a comprehensive investigation of the biomechanics of prophylactic knee bracing during landing using experimental data in conjunction with detailed computer models of the musculoskeletal system. Three-dimensional motion and force place data were collected from fifteen recreational athletes executing three different landing maneuvers: the double-leg drop landing, the single-leg drop landing, and the stop-jump landing, which were also performed with a prophylactic knee brace. In general, recreational athletes changed their lower-extremity kinematics and kinetics when wearing a knee brace and adopted an energy absorption strategy that could help protect the knee joint and reduce the risk of ACL injury during landing. The landing experiments were simulated using a rigid body musculoskeletal model in order to quantify the effect of a prophylactic knee brace on lower-extremity muscle function, which cannot be non-invasively measured in-vivo. Significant changes in the magnitude of peak muscle forces were observed, suggesting that prophylactic knee bracing alters muscle function. However, evaluating these changes with a representative anatomically-based finite element model of the knee joint revealed that the peak ACL force was not different in braced and unbraced knees. Overall, these findings provided further insight into the effectiveness of prophylactic knee bracing for preventing knee injury. This study was one of the first to develop a robust and comprehensive protocol to evaluate prophylactic knee bracing, from the joint level to the underlying muscle forces. While computational models form an invaluable tool for understanding human movement, they also highlight the complex interactions between the internal and external forces that provide stability to the knee. As biomechanics research continues to investigate the mechanisms of ACL injury and with more focused attention directed towards knee bracing, the sports medicine community will be better able to assess the benefits of prophylactic knee bracing