It takes about three months for a patient to recover from a knee cruciate ligament injury after reconstructive surgery, because after the cruciate ligament reconstructive surgery, the ankle flexion and extension weight-bearing activities must be restricted for 4-6 weeks before the patient can perform functional exercises of ankle flexion and extension and light weight-bearing activities on the ground. Generally, it takes 4-6 weeks of functional exercise before the affected limb can resume normal flexion and extension activities and normal life and work can be resumed. After the cruciate ligament reconstruction surgery, it is important to actively perform functional exercises for knee flexion and extension and leg muscle strength exercises to avoid affecting the normal flexion and extension activities of the affected limb at a later stage.