Injuries to the ligament and other supporting structures of the knee joint are becoming very frequent because of the increasing popularity of sports and the complexity of traffic and industrial accidents in the modern society. Vast knowledge of the anatomy, function and biomechanics of the knee joint together with the mechanism of its injuries have been recently documented. To obtain complete recovery of the injury as a goal, early diagnosis, prompt definite treatment, sufficient time of immobilization and well planned strenuous exercise are important. The clinical analysis of 28 patients with 31 knees by the concept of knee instability and preliminary result of treatment were reported. Through combined operative and conservative treatment, excellent and good were obtained in 96.8 percent.