Not long ago, the famous footballer Lionel Messi was unfortunately injured during a game and was reportedly diagnosed with a medial collateral ligament injury, or at least 8 weeks out of action. The medial collateral ligament (MCL) is an important structure on the medial side of the knee, whose main function is to limit excessive knee valgus. Injury to the MCL can be triggered by violent lateral shearing forces on the knee during some sports activities. Because the MCL is an extracapsular structure, swelling may not be as severe as in an ACL injury, but severe pain and localized tenderness can be highly suggestive of an MCL injury! Some people may even hear a ringing sound at the time of an MCL injury. When an MCL injury occurs, try to do pressure bandaging, icing, and bracing as soon as possible at the scene, before going to the hospital for the next step. For mildly injured MCL, the lateral move test may not be very obvious, but if there is a clear sense of “openness” in the lateral move, the MCL fracture can be basically determined. On imaging, MCL damage is not directly observed on X-ray unless there is some avulsion fracture. In the early days, radiology would indirectly determine MCL fracture by applying lateral shear stress to the knee while taking an x-ray, causing an “opening” on the medial side of the knee. However, with the rapid development of MRI (magnetic resonance imaging) technology in recent years, this method has been gradually replaced, and MRI is a very important test after MCL injury because it can visualize the damage to soft tissue structures. The direction of treatment varies depending on the degree of MCL injury. Generally speaking, for mild MCL injuries that do not involve functional structural changes, conservative treatment such as rest and braking can be chosen. For MCL rupture, the location and degree of injury should be determined, for example, if the injury is in the upper stop position, sometimes conservative treatment with a cast can be chosen. For example, if the injury is in the upper stop position, sometimes conservative treatment with a cast can be chosen. For the lower stop position, due to the blood supply and biomechanical factors, surgery needs to be actively considered at an early stage in most cases. I am a fan myself, and I have many friends around me who have had MCL injuries, many of whom are professional players. I often tell people that the rehabilitation process after an injury must be done in a scientific way. I know many friends who love to play soccer, during the brake itch, private removal of the cast or brace, on the field to “touch the ball”, the result of secondary injuries, or even more serious injuries, some professional athletes even retired because of this tragedy, which happens from time to time. In fact, not only for MCL, for any kind of injury, we should pay attention to the injury in the early stage should be to the regular hospital for examination, do not delay the best time for treatment. During the treatment period, should also strictly follow medical advice, to heal the injury, but also to carry out some joint mobility, muscle strength, proprioceptive training, only in the body to restore the normal level, we can feel at ease on the field of play!