Based on the knee MRI, the degree of cruciate ligament injury can be determined, which is categorized into three grades: grade I is that there is injury to the ACL signal within the MRI, but the integrity of the ACL is good; grade II is that there is injury to the ACL signal, with a partial disruption in the integrity of the ACL signal; and grade III is that there is injury to the ACL signal, and there is a complete rupture of the ACL. The degree of injury can also be differentiated according to the stability of the knee, which is categorized into stable and unstable injuries. Instability injuries are further divided into mild, moderate and severe. Mild instability injury can engage in general sports, such as jogging, but can not engage in certain sports, such as jumping up and landing on one foot, or using the affected leg to support the healthy foot to shoot the goal and other actions can not be completed or take a certain amount of time to complete the movement, and the ability to exercise is significantly reduced; moderate instability injury, the patient does not dare to run fast, or can not be able to stop and turn sharply during the running process, can not be one-legged jump; Severe instability injury means that during walking or jogging, the distal thigh and proximal calf will have obvious frustration.