The anterior cruciate ligament (ACL) rupture can be judged in five ways: First, by the feeling at the time of injury: if the thigh bone and calf bone of the knee joint feel a sense of contusion with each other (or the two bones wobble a little bit with each other) at the time of injury, the ligament can be judged as broken basically without the need for a doctor to check the body. Second, by feeling whether the joint is unstable: in running and jumping, rapid turning and stopping and sudden acceleration when running there is a shaking of the thigh and calf, or incoherence, or the feeling of not being able to use the force. III. Any repeated sprains: For patients who have been injured for some time, there are repeated sprains of the knee joint. IV. Magnetic resonance imaging (MRI) findings: shows an ACL fracture. However, the angle and position of the MRI projection and the projection conditions and the resolution of the machine are different, and the doctor’s experience in reading the film is different, which will affect the results of the film reading. The accuracy of the doctor’s examination varies greatly. The accuracy of the experienced doctor’s examination can reach more than 95%, but the inexperienced doctor may only be about 30%. When the patient is relaxed, the accuracy of the same doctor’s body check is good. The opposite is not true.