The MCL stands for the medial collateral ligament, which is one of the ligaments in the knee joint. It is a tough, flexible band of tissue that connects the bottom of the thighbone (femur) to the top of the shinbone (tibia) on the inner side of the knee. The MCL helps keep the knee from moving side to side. An MCL injury can range from a mild sprain or partial tear to a complete tear. The injury can be caused by getting struck in the knee or by bending or twisting the joint too forcefully, causing the ligament to stretch and tear. Wear and tear of the ligament over time through repeated stress and pressure, such as lifting heavy objects, can also cause injury to the MCL. Symptoms of an MCL injury include pain, swelling, stiffness, and unsteadiness, locking or catching in the joint. Most MCL tears do not require surgery, and non-surgical treatments such as anti-inflammatory medicine, ice, crutches, brace or splint, and physical therapy are effective in treating MCL tears. Recovery time for an MCL injury depends on the severity of the damage, but on average, these injuries take six weeks to heal.