For the grading of medial collateral ligament injury, it can be divided into three degrees according to the MRI performance and clinical examination, i.e., degree I, degree II and degree III. If the ligament signal is only abnormal on the MRI and there is no interruption of the integrity of the ligament, the ligament is relatively intact, which is a degree I injury. Grade II injury is a partial ligament injury with abnormally high ligament signals and partial ligament tears, and the joint is more stable at the time of examination. Grade III is a complete rupture of the ligament and a significant interruption of continuity on MRI, and the joint is clearly unstable on examination, which often requires surgery.