Anterior cruciate ligament (ACL) injury is one of the common knee injuries. With the development of society, the improvement of China’s competitive sports level and the widespread development of mass sports, ACL injury of the knee occurs more and more in sports trauma, the early post-injury clinical diagnosis is difficult due to knee swelling, pain and muscle spasm, most patients with acute traumatic knee hematoma of ACL injury are misdiagnosed in emergency and outpatient clinics and delayed as old ACL injury, resulting in some Most patients with acute traumatic knee hematoma are misdiagnosed in emergency and outpatient clinics and delayed as old ACL injury, leading to some complications before they come to the clinic and miss the best treatment time. Patients often present with knee instability and some have secondary meniscal injury or articular cartilage injury. More than 70% of patients with acute traumatic knee hematoma have ACL injury, the incidence of which is reported in foreign literature is quite high, more than 150,000 people in the United States have ACL injury every year, and the number of annual incidence is increasing, there are no specific statistics on the number of incidence in China, but there are reports that the overall prevalence of ACL injury in active training athletes in China is 0.47%, and the general population in fitness sports ACL injury is also increasing. ACL injury is a serious knee trauma, if not treated in time, knee instability often occurs, and easy to secondary meniscal damage, articular cartilage damage and traumatic arthritis and other lesions, so that the patient’s knee function is significantly reduced, seriously affecting daily life and sports, so that athletes shorten or even This can seriously affect daily life and sports, shortening or even losing athletic life. The early arthroscopic ligament reconstruction for ACL injury can restore the normal function of the knee joint, so the diagnosis and treatment of ACL injury should be clarified as early as possible. After ACL injury, due to the rupture of synovial vessels on its surface, blood flows into the knee cavity, and the knee joint generally swells significantly within 2 h after the injury, which produces significant knee pain and protective spasm of the thigh muscles due to the stimulation of the synovial membrane of the knee by the intra-articular hematoma. The diagnosis of ACL injury can be clarified by performing a positive anterior drawer test and Lachman’s test before significant swelling of the knee occurs after the injury. The axial shift test is not advocated for acute ACL injuries because it can significantly aggravate the patient’s pain with a high false-negative rate when repeated injury movements are examined. When the swelling of the knee joint is obvious and the patient has significant pain and protective muscle spasm, it is difficult to detect positive signs of ligament injury. At this point, MRI or arthroscopy is feasible to clarify the diagnosis.