The lateral collateral ligament (LCL) is one of four major ligaments that support the knee joint. It connects the femur to the tibia: it goes from the top of the tibia to the lower section of the femur. Its function is to prevent lateral mobility of the knee joint and to keep the outer side of the joint stable. The most common injuries occur through pressure or an injury that pushes the knee joint from the inside, which results in stress on the outer part. The symptoms of a rupture or tear of the lateral collateral ligament are: swelling of the knee, the knee blocking during movement, pain or tenderness on the outer side of the knee, and instability in the knee. An examination of the external lateral ligament should be performed to study the possible lateral laxity. The examination bends the knee by 25 degrees and exerts pressure on the inner surface. X-rays of the joint, an MRI, and other studies should also be carried out. The patient should apply ice on the area, in addition to taking anti-inflammatories, elevate the knee and cease physical activity until the pain and swelling disappear.