ACL injury mechanism in alpine skiing: analysis of an accidental ACL rupture

Knee injuries in alpine skiing, especially the rupture of the anterior cruciate ligament (ACL), are still the leading indication for surgical treatment. The boot-induced anterior drawer (BIAD) caused by the backward fall is one of the possible injury mechanisms. We investigated the landing of approximately 250 jumps to collect data for a computer model of the BIAD. During our experiments one test subject suffered an ACL rupture of his right knee. This accidental event was recorded on video for later 2D motion analysis. Furthermore, the muscle activity of four muscles (vastus medialis and lateralis, biceps femoris and semitendinosus) was registered for both lower extremities during this event. Seven more subjects were analyzed under identical experimental conditions, thus representing an adequate reference group. The results of the 2D motion analysis will be presented and compared to the results of the reference group. Further, the registered EMG signal of the injured subject will be illustrated and discussed in relation to a reference subject. Our observations allow the conclusion that during landing situations different kinematics besides those described for the BIAD, in combination with certain muscular conditions, may lead to an ACL rupture.