Objective:To establish the rat knee osteoarthritis model by partial patellar ligament defect combined with medial collateral ligament transection. Methods30 SD rats were randomly divided into the blank group, 3-week model group and 6-week model group, 10 rats in each group. The rats in the 3-week model group and 6-week model group were performed the operation to induce the partial patellar ligament defect and medial collateral ligament transection. The rats in the blank group were only cut the skin to expose the patellar ligament and medial collateral ligament, without other surgical treatment. One week after surgery, the rats were forced to exercise for 30 minutes per day. 3 weeks and 6 weeks after modeling,the rats were sacrificed respectively,and the knee joint was dissected. The articular surface of the patella and the femoral condyle were exposed to observe the morphological changes,and the cartilage morphology of femoral condyle articular surface was evaluated by Pelletier’s principle. The samples of knee joint were collected,and the pathological sections were stained with safranin O-fast green and Alcian blue to observe the morphological structure of cartilage by light microscopy,and the degree of degeneration was evaluated by modified Mankin’s score.  Results:The degeneration of knee joints with different degrees were observed in the 3-week and 6-week model groups,and the Pelletier score and modified Mankin’s score in these two groups were higher than those in the blank group (P<0.05),and the scores in the 6-week model group were higher than those in the 3-week model group (P<0.05).  Conclusion:The rat knee osteoarthritis model can be effectively established by the partial patellar ligament defect combined with medial collateral ligament transection. The histological changes are consistent with the pathological features of osteoarthritis cartilage degeneration,and the operation is simple with small traumas and low infection rates,which is an ideal modeling method.