The ligament on the outside of the knee is called the lateral collateral ligament of the knee. The lateral collateral ligament of the knee, also called the fibular collateral ligament, is a cord-like tough fibrous cord that originates from the lateral epicondyle of the femur and extends downward to the head of the fibula, and most of the surface of the ligament is covered by the biceps tendon, which is not directly connected to the lateral meniscus. Injury to the lateral collateral ligament of the knee joint can cause local pain and tenderness, and some patients may have subcutaneous swelling. In addition, due to the injury of this ligament, the protection and restriction of the knee joint is weakened, and a sense of instability may occur when the patient moves the knee joint, and the lateral side of the knee joint will show obvious pain symptoms during the lateral compression test. Lateral collateral knee ligament injury can be diagnosed by MRI, and after the diagnosis is clear, timely treatment should be carried out under the guidance of doctors to avoid further aggravation of the injury.