Surgery for anterior cruciate ligament (ACL) rupture of the knee has been controversial in the past few years, especially since many doctors in China advocate that the earlier the surgery, the better. But how early is early enough? Some people think that it is bad to be hospitalized for surgery immediately or a few days after an acute rupture, and that it is bad to be late with meniscal damage, cartilage degeneration, etc. Some people also think that premature surgery will aggravate intra-articular adhesions and cause difficulties in postoperative functional exercise. The following, combined with my personal clinical experience over the past few years, as well as the literature I have read, especially in foreign languages, I would like to briefly introduce to you some of my views on the timing of surgery, for reference only! After an acute rupture of the ACL, there is intra-articular bleeding, the ruptured ligament retracts, and the inflammatory cells in the joint are active and try to wrap around to repair it. If the tendon is then implanted, either autologous or allogeneic, the intra-articular inflammatory response to the graft is initiated (stronger for allogeneic, weaker for autologous), so that the intra-articular scar response will be more pronounced and the patient’s post-operative functional exercise will be much more difficult, which is the main reason why many English literature opposes surgery in the acute phase. A large number of clinical cases confirm that more than 90% of all cases with poor flexion angle exercises are those operated in the acute phase (tentatively positioned at 1 month), and very few in the subacute (1-3 months) and slower (3 months) phases are extremely difficult to exercise, unless the postoperative period is too long to start exercising. So, is it true that delaying surgery can cause rapid joint degeneration? The answer is no. Over the decades of life, the knee joint is subjected to an uncountable number of activities and stresses. Would a patient who knows that he or she has torn ligaments in the knee and is waiting for the surgery period go to great intensity to exercise and thus damage the knee joint? Therefore, a short rest for a few weeks after the injury, waiting for the acute inflammatory period of the joint to pass, reducing activities and avoiding sports will not have a great impact on the cartilage and meniscus in the joint. Based on the above two points, my opinion is clear: after the diagnosis of ACL rupture, surgery in the acute phase is likely to cause difficulties in postoperative functional exercise, but too long is likely to cause increased degeneration of intra-articular structures, therefore, it is recommended to operate in the subacute phase (1-3 months). In the following cases, ACL fracture should be operated in the acute phase 1. Fracture of the lower stop of ACL, i.e., fracture of the intercondylar ramus of the tibia. Because of the ligament contracture after the acute phase, the fracture is difficult to reset; and the fracture end is smooth and rounded, making it difficult to heal. 2. Combined lateral collateral ligament injury that requires repair. Such as complete rupture of the medial collateral ligament, osteochondral avulsion fracture of the lateral collateral ligament femoral epicondyle, and avulsion fracture of the fibular head. Because of these injuries after the acute phase, the lateral collateral ligament retracts and will not be able to be pulled back for repair. 3, combined with huge meniscal tears, especially barrel shank tears, joint interlocking. In the acute phase of this injury, an experienced arthroscopist will try to suture the torn meniscus, but of course it may not always work as expected. However, if the surgery is delayed, the chances of suturing will undoubtedly be greatly reduced.