Objective To investigate the clinical effect of chitosan in prevention of knee dysfunction due to adhesion after operation for patellar fracture. Methods From March to October 1999, 40 cases of patellar fracturewere treated by internal fixation, with intraarticular injection of 2% chitosan in only 24 cases after fixation and with no chitosan injection in 16 cases(control group). The function of the knee joint, including extension and flexion, was evaluated 1month and 1 year after operation respectively. Results One month after operation, the knees with chitosan injection could actively move in the average range of 104°±23°, and the knees in the control group could move in the average range of72°±16°, which showed significant difference between two groups(P＜0.01); 1 year after operation, the range of movement of the knees with injection was 165°±38° on average, and that of the knees in the control group was 110°± 31°, which also indicated significant difference between two groups (P＜0.05). Conclusion Medical chitosan could effectively prevent or reduce the post-operative adhesion of knee joint after patellar operation.