Anterior cruciate ligament injury of the knee is usually difficult to heal on its own, and it takes about 9 to 12 months to recover the ability to exercise through standardized treatment, but the specific recovery time is not uniform due to individual and disease differences. If there is no combination of other structural injuries, just a simple ACL injury, the patient can gradually restore the range of motion of the knee according to the rehabilitation program, train the knee joint proprioception, train the muscle strength as early as possible, and can walk on the ground appropriately, which takes about 9 months. Severe patients must wear a brace. If the patient has other injuries in combination, such as meniscus injury, the impact of meniscus injury on postoperative rehabilitation should be considered, and an appropriate rehabilitation program should be adopted according to the doctor’s guidance, which will take about 12 months. Patients with ACL knee injuries must actively follow their doctor’s instructions for treatment and rehabilitation to minimize the adverse effects of the disease.