Kinematics Based Knee Moment Prediction for Video Analysis of Anterior Cruciate Ligament Injury

Abstract

BACKGROUND: Anterior cruciate ligament (ACL) is frequently injured during sports activities with abducted and rotated knee position, indicating that huge external force is causing such out of plane knee kinematics. For ethical reason, it is impossible to measure knee dynamics in injury situation. However, if we predict the knee moment based only on kinematic information, we may be able to quantify the knee loadings by analyzing ACL video sequence. We had proposed a kinematics-based model for knee moment calculation at last ACSM's meeting and experimentally confirmed its accuracy (2009). In this study, we then apply this model to injury video analysis. PURPOSE: To determine the knee loadings at ACL injury from previously filmed injury video. METHODS: A video of an ACL injury situation, that a handball player suffered her ACL at a landing from a jump, was utilized. A written permission was obtained from both the player and Japanese Handball Association for the use of this video. A three dimensional Cartesian coordinate was reconstructed based on the known geometries, e.g., court lines and goal posts, filmed in background. The positions and the orientations of the player's body segments were obtained by fitting a skeletal figure to the player's silhouette. The ground reaction force and its acting point were calculated with the acceleration of body center of mass. The segmental masses and those positions were estimated from Chandler et al.(1975). The knee moment was then calculated using the kinematics-based model. RESULTS: A peak knee abduction moment of 460 Nm was observed at about 100 ms after foot impact. Previous cadaveric data supported that the peak value of knee abduction moment exceeded the knee mechanical tolerance. CONCLUSIONS: Findings suggest that the knee experienced an increased abduction moment at the time of ACL injury. This study showed a possibility to quantify the direct mechanism of ACL injury that cannot be evaluated in lab study. Future work is required to understand how we decrease knee loadings for injury prevention. Supported by the Ministry of ESCST Japan, Grant-in-Aid, 21700667,2009.