If the cruciate ligament of the knee is torn, surgical treatment is usually required for cruciate ligament reconstruction. If surgery is not performed, it can cause instability of the knee joint, which can accelerate the degeneration of the joint. Post-operative functional exercises are usually performed after the ACL reconstruction to accelerate the recovery of the knee joint. In the first month after surgery, a hinge brace should be worn. Under the protection of the brace, the knee joint can be moved appropriately and a small amount of weight can be put on it. Generally, running sports can only be performed 3-4 months after surgery, and most athletes can start professional sports only after 6 months.