ACL reconstruction generally involves making a graft from an autologous tendon, then inserting the graft into the joint and using the graft to connect the two lower extremity bones, the femur and tibia, thereby restoring stability to the joint. However, in order for the graft to function properly, it needs to firstly have a reliable healing of the graft to the bone, and secondly, its fibrous component needs to change from tendon fibers to reliable ligament fibers, and the latter is a complex and more important process, so that the post-operative rehabilitation exercises are very important, and the surgery is only the beginning of the treatment. When the graft is first implanted in the joint, necrosis can occur due to ischemia. In the early stage of ischemic necrosis, the collagen fibers of the graft have not disintegrated and the strength of the graft is still present; next, the collagen fibers of the graft will disintegrate and the strength of the graft decreases; then the surrounding blood vessels grow in, the graft begins to vascularize, the collagen fibers begin to remodel, and the strength of the graft is gradually restored. The strength of the graft is lowest in the late stages of graft necrosis and early stages of vascularization. In humans, this period generally corresponds to 4, 5, and 6 months after surgery, and in individuals this period may be longer. Without stress stimulation, the tendon fibers of the graft will not become ligament fibers, but will become disorganized collagen fragments with very low strength and will not be able to function as a ligament. However, excessive stress stimulation can cause the weaker graft fibers to rupture during the shaping process. Therefore, special attention is given to the 4-6 months in the postoperative rehabilitation program, which is designed to both stress stimulate and protect the reconstructed ligaments. Therefore, it is important not to over-range training and start sports programs too early in this phase; some people do training according to the prescribed program but seriously overtime; some people just show excessive daily walking time, especially brisk walking time. The end result is the same, that is, the grafts do not pass the shaping phase and fail. Therefore, in the 4-6 months after surgery, firstly, you should strictly follow the rehabilitation program and do not go over the range; secondly, you should strictly follow the rehabilitation time and do not go over the amount; in addition, do not walk too fast for a long time. In order to protect the ligaments during the ligament shaping phase, the use of anterior cruciate ligament injury brace is recommended in Europe and America. This brace is specially designed to prevent excessive stress on the reconstructed ACL by applying resistance when the knee is close to extension; it protects the reconstructed ligament while ensuring completion of the rehabilitation program and even more aggressive rehabilitation. The brace is suitable for patients who need to perform an excessive amount and range of motion, i.e., who want to exercise as early as possible, as well as for patients who need to walk for long periods of time and too fast in their daily lives. In recent years, this type of brace has been introduced to China (such as the American DJO brand), but because it needs to be customized according to the patient’s leg shape, which is slightly troublesome and expensive (about 3000 RMB), it is currently used only by some athletes and has not yet become a popular product, and similar products are available in China. The purpose of ligament reconstruction is to use the ligament for the rest of your life, do not love sports, too hasty, resulting in ligament failure, to strictly follow the rehabilitation program, neither too hasty nor completely without exercise.