The ACL is a relatively common clinical sports injury commonly seen in sports enthusiasts, such as soccer, basketball, and badminton. In the United States, approximately 100,000 ACL ruptures occur each year, and approximately 75,000 individuals undergo initial ACL reconstruction surgery, requiring surgical treatment in 75% of cases. The natural course of a partial ACL injury varies depending on the extent of the injury, the patient’s level of motion and the severity of instability symptoms. Partial ACL injuries usually take 3 months to recover with satisfactory functional recovery. However, there are still some patients with partial ACL injuries who continue to have symptoms of knee instability, and these patients require close clinical follow-up and full physical therapy and, if necessary, ACL strengthening reconstructive surgery to restore knee stability. The natural course of a complete rupture of the ACL has a poor outcome. After a complete rupture of the ACL, some patients are unable to perform sharp stops, directional changes, rotations and other types of sports, and some even experience symptoms of instability during daily walking, such as “weak legs” and joint misalignment. After a period of time, the muscles around the knee joint atrophy. Very few patients have no symptoms of instability at all after a complete ACL rupture. About half of the patients with ACL injuries have combined meniscal, articular cartilage or other ligament injuries. Even if the ACL injury alone is left untreated, many patients will experience secondary meniscal injury and articular cartilage surface wear at some point after the injury. After an ACL injury, approximately 90% of patients will experience meniscal wear or damage within 10 years of injury due to the chronic instability left in the knee joint, and similarly without ACL protection, more than 70% will experience severe articular surface wear within 10 years of injury. With the ACL intact, along with the other intra- and extra-articular ligaments and muscles and the meniscus, the knee joint moves in a regular pattern according to a set trajectory. A joint that moves along a normal trajectory will not have its articular surfaces worn down. Once the ACL is ruptured, the trajectory of the knee is altered and there is a severe imbalance in the forces on the joint surface, resulting in severe wear and tear of the articular cartilage, leading to traumatic arthritis. Normal articular surface cartilage and meniscus Secondary meniscal injury after cruciate ligament injury Secondary wear of the articular surface after cruciate ligament injury ACL conservative treatment measures include advanced physical therapy, reasonable rehabilitation, and wearing protective braces. Which patients can be treated conservatively? 1.Patients with partial injury and no symptoms of instability. 2.Patients who are completely injured, but have no symptoms of instability and pain in daily life and are willing to give up sports. 3.Patients who have been engaged in manual labor for a long time or living in a sitting position for a long time. 4.Children whose growth plates are not yet mature. 5.Patients who are older and have already had significant degeneration of the joint surface. Which patients with ACL rupture need surgery? Patients with knee instability or presence of knee pain; young people (usually younger than 55 years old, but surgery can still be considered if older but without degeneration of the articular cartilage); hobby sports; and those without or with only minor degenerative changes in the knee joint.