The anterior cruciate ligament is an unusual ligament. Why? There are many ligaments in the knee, not to mention others, but the ACL and the posterior cruciate ligament are in the center of the joint, while the others are around it, the difference between central and local. The reason it is called the cruciate ligament is because it forms a cross structure with the posterior cruciate ligament and has a cruciform appearance, or as some doctors call it, the anterior cruciate ligament. The anterior cruciate ligament begins on the medial aspect of the femoral epicondyle and ends on the medial aspect of the intercondylar spine of the tibia in an anterior and inferior oblique line. It originates from the ventral germinal base and is gradually shifted posteriorly during growth. It begins to form at 8 weeks of fetal age and begins to divide at 16 weeks. By adult age, it has an average length of 37 mm and an average diameter of 12 mm and is divided into two bundles, the anterior medial bundle and the posterior lateral bundle, with the posterior lateral bundle being shorter and smaller. As seen in the figure, the ACL is not a homogeneous structure and is scalloped at the superior stop, with the stop of the anterior medial bundle being superior. In contrast, there are two types of tibial stops, one with anterior-internal and posterior-external bundle stops in an anterior-posterior distribution and one with a left-right relationship. Understanding these is important for understanding the treatment. So just how strong is this ligament? The average rupture load strength for adults is 1600 Newton, what a concept, we all know Yao Ming, 2 meters 27 meters tall, weight is 140 kg, then we can use the ACL to lift him easily without fear of rupture, provided you have the strength. As mentioned before the ACL is not ordinary, not only in the general body, but also in the microscopic. The ACL, with the word anterior in its full name, so its most important role is to prevent the tibia from moving forward, and it plays a role in 85% of the forward limiting force. If there is too much external force that causes an ACL injury, you will see a significant forward movement of the tibia when the patient is subjected to a forward pulling force. The second function is to prevent internal and external rotation of the knee joint, and it plays a different role with a different focus in different angles of knee flexion. In flexion, both are relaxed and the ACL plays a leading role. The third function, the control of knee rotation, is that the knee can rotate in flexion, and the ACL does not travel vertically, but obliquely, and plays a role in controlling rotation. The last function is that the ACL has nerve receptors within it that can sense changes in position, so it has a proprioceptive function. In conclusion, the ACL is an important structure in maintaining the stability of the knee joint, and it works with other ligaments to allow the knee to move properly. The ACL is a special ligament that is divided into two bundles and is very strong. It is very important in maintaining the stability of the knee joint. The most common mechanism of injury to it is flexion valgus external rotation injury. ACL injury is a serious consequence of the disease, and the damage to the patient’s motor function is severe. The ACL is a unique stabilizing structure within the joint that serves as the core of anterior-posterior stabilization, and the consequences of injury are severe. It is a real nightmare for sports injuries.