The Medial Collateral Ligament (MCL) is a key ligament located on the inner side of the knee. It connects the thigh bone, or femur, to the shin bone, known as the tibia. The MCL helps stabilize the knee joint, preventing it from bending inward and providing support during activities like walking, running, and jumping. Injuries to the MCL are common in sports, often resulting from sudden twists or impacts. Symptoms of an MCL injury may include pain, swelling, and difficulty moving the knee. Treatment typically involves rest, ice, compression, and physical therapy to restore strength and flexibility.