COMPUTER-SIMULATION OF LANDING MOVEMENT IN DOWNHILL SKIING - ANTERIORCRUCIATE LIGAMENT INJURIES

Anterior cruciate ligament (ACL) injuries typically occur in high-spee d downhill skiing during the landing phase following a jump. A direct dynamics simulation;model was developed which allows investigation of possible ACL injury mechanisms without the need to use actual skiers i n a potentially dangerous environment. The model included multibody dy namics, muscle dynamics and a model for ski-snow interaction. The mode l's ability to reproduce an actual landing movement was investigated b y minimizing the differences between measured and simulated landing mo vements as a function of constant muscle stimulation levels. The remai ning difference was mainly due to noise in the measurements. A small b alance disturbance was induced to simulate an injury condition. This d isturbance caused the modeled skier to fall slightly backwards. A reco very attempt was made by maximal activation of the quadriceps and ilio psoas muscles. Peak resultant shear force at the knee joint in ACL dir ection was substantially higher in the injury simulation (100 N) when compared to the simulated normal landing movement (589 N). Taking into account quadriceps contraction and orientation of the ACL with respec t to tibial plateau, peak ACL force during the injury simulation was e stimated to be 1350 N, which is within the range of failure loads for this ligament. The external forces were mainly (75%) responsible for t his loading. The contribution of the fully activated quadriceps muscle s was only 25%. It was concluded that the model could reproduce a typi cal landing movement and is therefore considered to be sufficiently re alistic. Second, the simulation results suggest that external forces a re the main cause for ACL injuries during landing movements in downhil l skiing. Copyright (C) 1996 Published by Elsevier Science Ltd.