According to Medline Plus, MCL stands for medial collateral ligament. The MCL is located on the inside of a human knee. It connects the lower, inner surface of the thigh bone to the upper, inner surface of the shin bone. It also prevents the knee from bending inward.
WebMD reports that MCL injuries usually occur when the knee is utilized during strenuous activities. Bending, twisting or changing direction quickly increase the likelihood of an MCL injury. Minor MCL injuries can heal with rest, ice treatment and use of over-the-counter anti-inflammatory medication. More severe cases require professional medical attention. Symptoms of MCL injuries include knee tenderness, pain or swelling.