There are two important ligaments within the knee joint, the anterior cruciate ligament and the posterior cruciate ligament, which are important stabilizing structures during knee motion. ACL injuries are more common and can occur alone or in conjunction with other structures in the knee joint. 1. How do ACL injuries occur? Most patients will have a significant history of knee injury, which can be divided into contact and non-contact injuries. Contact injuries include: internal and external knee injuries, knee hyperextension injuries, and anterior – posterior knee injuries. Non-contact injury is a common mechanism of injury in sports, mostly seen in runners stopping sharply, changing direction or landing in the jump. 2.What is the manifestation after an ACL injury? Acute ACL injury will have a history of trauma as described above. The injury may be accompanied by the sound of intra-articular tearing, followed by pain, swelling and joint instability of the knee joint, and the inability to complete ongoing movements and walk. The patient’s complaints and history of injury are very important. If the patient has a clear history of knee trauma accompanied by knee swelling, pain, and dysfunction, a cruciate ligament injury of the knee should be highly suspected. Even if the swelling subsides, the pain subsides, and the patient can continue to walk and run after the injury, the patient may experience joint instability, repeated sprains, or be afraid to pop up and land on one knee, or have joint “clicking” symptoms, which are all symptoms of ACL injury. 3.Why is ACL misdiagnosed? It is mainly related to the level of awareness of the first consulting physician, sports medicine is a relatively new discipline in traditional orthopedics. When a joint is sprained, if the x-ray does not show a fracture, it is easy to hastily diagnose it as a “soft tissue injury” and go home to give physical therapy and massage, and when the swelling disappears, both the doctor and the patient are happy. In fact, as long as the knee joint is swollen after the injury, there should be high suspicion of intra-articular ligament rupture or osteochondral damage and bleeding, and these injuries will not heal on their own, and will be followed by injuries to other structures in the joint such as the meniscus, neglecting the condition and delaying treatment. 4.How to treat anterior cruciate injury? At present, regardless of the acute injury or chronic injury of anterior cruciate injury, the diagnosis is clear advocates early surgery, in addition to the stop point avulsion fracture for fracture repositioning and fixation, ligament rupture surgery also need to carry out anterior ligament reconstruction. Previous arthrotomy reconstruction and ligament suturing with poor clinical results have rarely been used. With the development of minimally invasive arthroscopic surgery, arthroscopic reconstruction of the ACL has become mainstream. Arthroscopic surgery is less traumatic, with fast recovery and excellent clinical results. 5.What are the advantages of treating anterior cruciate injury? At present, our department adopts the internationally popular “single bundle ACL double fixation surgery”, and the reconstruction material mostly adopts the autologous N cord tendon four-strand reconstruction, and the femoral side and tibial side are double fixed, which can allow the patient to perform joint functional exercise early and avoid complications such as joint adhesions and quadriceps muscle atrophy. In addition, the secure fixation also improves the healing rate between the tendon and the bone tract and increases the success rate of the procedure.