ACL injury is a common sports injury to the knee joint, mostly seen in sports activities and traffic accidents, such as: soccer, basketball, volleyball, ice skating, skiing, badminton, etc. Knee sprains or sudden folding movements during jumping and landing during sports are likely to damage the ACL, commonly seen in adolescents who love sports. In addition, with the increase in the number of cars, the number of ACL injuries caused by traffic accidents is also increasing. In the United States, approximately 100,000 ACL ruptures occur each year, and approximately 80,000 people undergo initial ACL reconstruction surgery, requiring 80% of surgical treatment. The injury is felt as a misalignment of the joint, sometimes with a rattling sound of a tear inside the joint, and the patient usually falls to the ground and is unable to stand up immediately. Return to activity is often unlikely and walking is often difficult. Because ligament injuries are often accompanied by intra-articular hemorrhage, there is significant joint swelling, which affects joint motion and walking. In this case, the likelihood of ACL injury is greater than 70%. If there are four key words to summarize the clinical manifestations of an ACL injury in the acute phase, they are “loud, painful, swollen, and limited”. ACL injury may also be associated with or secondary to meniscal injury, with symptoms of joint locking. After a complete rupture of the ACL, some patients are unable to perform sports such as stopping, changing direction and rotating, and even some movements in daily life, such as turning, may cause symptoms of knee instability, such as “weak legs” and joint misalignment. Over time, the muscles around the knee joint gradually atrophy.