The medial collateral ligament (MCL) tears frequently in sports and is commonly accompanied by ACL and medial meniscus injuries. Experimental and clinical studies have been widely carried out, but were limited to obtaining stress distribution and conducting parametric studies. The purposes of this study were to develop a validated three dimensional finite element model of knee joint, and to analyze the subsequent changes of the kinematics and stress distribution of corresponding structures induced by different levels of MCL rupture. The model was developed from magnetic resonance images and validated by published experimental data. A loading and boundary condition of passive knee flexion (0∼60 degrees) were applied to the knee with an intact MCL, superficial MCL torn, deep MCL torn and complete MCL torn. The most significant differences found were the deformation within medial meniscus as well as the valgus degree of the knee between pre- and post-injury MCL condition. The computational results indicated that the deep MCL prevents excessive translation of medial meniscus, while the superficial MCL provides most of the restraining valgus moment. This study could help to understand the various subsequent injuries led by MCL injuries, and to predict the risk positions in the joint. Furthermore, this model could shed some light on the mechanism of MCL injuries and the treatments.