The patient underwent reconstruction surgery for ACL injury and needed to wear a brace to immobilize the patient while sleeping after the surgery. Because the lower limb muscles may spasm and contract when the patient sleeps, which will pull the knee joint to produce flexion and extension activities, which will easily lead to secondary rupture of the reconstructed cruciate ligament, so the patient needs to wear a brace to give immobilization after the anterior cruciate ligament reconstruction surgery. Without affecting the healing of the ligament, early functional knee exercises can be carried out under the guidance of the rehabilitation doctor to restore the muscle strength of the knee joint, to prevent adhesion of the knee muscles, and to prevent stiffness of the knee joint and limitation of activities.