There are two important ligaments in the knee joint – the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), collectively known as the cruciate ligaments of the knee. The anterior cruciate ligament is a very important stabilizing structure in the knee joint, firmly connecting the femur and tibia, and in layman’s terms, is used to ensure that the calf and thigh do not sway back and forth. When is an ACL injury likely to occur? The ACL is very strong and is generally not prone to rupture. Ruptures usually occur during strenuous exercise (basketball, soccer, track and field, etc. are more common), sudden deceleration and change of direction while running or jumping, or as a result of rotational movement or landing of the knee. 75% of cruciate ligament ruptures are sports injuries. Beyond that are accidental injuries, including traffic injuries and falls. What are the signs of an ACL injury? Patients with ACL injuries usually hear a “thump” in the knee at the time of injury and then experience swelling in the joint, which can be tolerated after a short period of rest, but will be followed by constant swelling and pain in the joint. Once an ACL injury occurs, it is easy for the knee to become unstable, and the knee will not be able to exert any force, especially when walking up and down the stairs. Can ACL injuries be prevented? Of course it can! It is recommended to maintain the following good habits before exercise: 1. Reasonable warm-up preparation to increase joint flexibility to prevent injury. 2, maintain the correct posture during exercise, do not for the sake of winning the overly intense scramble. 3, wear professional protective gear at the right time to effectively protect the joints Once you suspect an ACL injury, you must stop exercising and consult a doctor in a timely manner, so that the professional doctor can determine the degree of ligament damage and decide whether follow-up treatment is needed.