Anterior cruciate ligament (ACL) injury is one of the common knee injuries. I. Clinical manifestations Some patients feel the sound of tearing in the knee joint during strong trauma, followed by weakness of the knee joint, severe joint pain, rapid swelling, blood accumulation in the joint, and subcutaneous bruising around the joint often indicate joint capsule injury and joint dysfunction. Patients with old injury may have quadriceps atrophy, a feeling of weakness (giving way) or misalignment, and decreased motor ability. Diagnosis When the above clinical manifestations are met, a positive anterior drawer test (ADT), a positive Lachman test, and a positive axial shift test may be seen during the doctor’s examination. Combined with X-ray and MRI examinations, the diagnosis is generally not difficult. Third, treatment Some studies have shown that ACL injury by conservative treatment, 1/3 of patients without joint instability, 1/3 of patients with instability during exercise, 1/3 usually have instability during activity. 1.Non-surgical treatment For simple ACL rupture or incomplete rupture, the affected knee can be fixed in flexion 30° position with a long-leg cast first, paying attention to pushing the upper end of the affected tibia backward before the cast is formed, and fixing it for 4-6 weeks. Start quadriceps training after 3 days of cast fixation. 2.Surgical treatment Currently, the classic surgical treatment for ACL rupture is arthroscopic ACL reconstruction surgery. The ruptured ACL can be replaced with an autologous or allogeneic tendon. Surgery should be considered in young patients with complete ACL rupture, combined with meniscal or other ligament injuries, who participate in sports at a high athletic level. Normal sports activities can be resumed basically one year after surgery.