Abstract: Meniscus and ligament ruptures are common in anteriorcruciate ligament (ACL) deficient knee. The mechanism of injuries is stillunclear, and was mainly inferred from ex vivo experiments and clinicalstudies. In this study, a three dimensional finite element model of kneejoint was reconstructed from magnetic resonance images. The geometry data ofthe knee from literature was used to validate the model. Tibial displacementand in situ force in ACL in response to the anterior tibial loads werecalculated and coincided with the published experimental data. Thesimulations of the models with and without ACL were performed under anteriortibial loads and axial tibial loads at 0^\circ and 30^\circ flexion. Our resultssuggest that ACL deficiency could lead to abnormal stress distribution: thestress near the posterior insertion of the medial meniscus increasedsignificantly; the changes of the stress in the lateral meniscus, posteriorcruciate ligament and collateral ligaments depended on the loads and theflexion angles. This study may help to explain the higher subsequent injuryrate of ACL-deficient knee, and to predict the injury risk positions in thejoint. Furthermore, this model could shed some light on the mechanism of ACLinjuries and the treatments.