ACL injury is a common sports injury of the knee joint, commonly occurring when the knee joint is sprained during jumping and landing during sports, the injury can be felt as a sense of joint misalignment, and sometimes a pop can be heard, after the injury there will be obvious joint swelling due to intra-articular bleeding, according to statistics, knee sprain with intra-articular hematoma, the incidence of ACL injury can be as high as 70%. After the injury, the patient has limited joint movement and difficulty walking. If we use four key words to summarize the clinical manifestations of ACL injury in the acute phase, it is “loud, painful, swollen, and limited”. ACL injuries may also be associated with meniscal and/or collateral ligament injuries, which may have other combined clinical manifestations. Fresh and old ACL ruptures differ in their clinical presentation. The main manifestations of fresh ACL rupture are: 1. Tearing of the ligament is accompanied by tearing sound and joint misalignment, intra-articular hemorrhage, resulting in joint swelling, pain, and most cannot continue to engage in the original movement, and even limited extension and hyperflexion; 2. Joint swelling: most patients with joint swelling have intra-articular ligament injury, and according to statistics, more than 50% of patients with post-traumatic joint swelling have ACL injury According to statistics, more than 50% of patients with post-traumatic joint swelling have ACL injury. 3. Positive floating patella test on physical examination, laxity and non-resistance on Lachman examination; 4. Nuclear magnetic examination of the knee suggests: intra-articular blood accumulation, swelling or interrupted continuity of the ACL, visible stump, lateral wall of the intercondylar fossa of the femur or the posterior aspect of the femoral epicondyle and corresponding bone contusion manifestation of the tibial plateau. ” The main manifestations of old ACL rupture are: 1, joint laxity and instability, the patient has a sense of knee joint misalignment or playing soft leg in sports, cannot stop and turn sharply, cannot use the affected leg for single-leg support; 2, the knee joint is easily and repeatedly sprained and painful during sports, and even repeated interlocking after causing meniscus injury; 3, unstable going downstairs, the patient dares not go downstairs, or has a sense of playing soft leg in going downstairs. Or a feeling of instability when jumping on one foot. 4, physical examination: Lachman examination relaxation without resistance, positive front drawer test; 5, nuclear magnetic examination of the knee joint suggests: the continuity of the anterior cruciate ligament is interrupted, the stump can be seen, the femoral epicondyle and tibial plateau bone contusion performance. In case of excessive time, the morphology of the ligament disappears and osteophyte manifestations appear. After a rupture of the ACL, if it takes more than 3 weeks and is not treated, it gradually turns into a chronic phase, which is characterized by knee instability, playing with a weak leg and a sense of joint misalignment during movement. Long-term untreated tears of the meniscus can lead to symptoms of joint interlocking.