Structure and function, injury, pathology, and treatment of the medial collateral ligament of the knee

The medial collateral ligament (MCL) is the most commonly injured ligament of the knee. There is a spectrum of injury severity, and injuries may be acute or chronic. The MCL is also frequently injured in conjunction with other knee structures. Clinical evaluation of the knee is important to assess the degree of surgical acuity, but magnetic resonance imaging can provide details about the injury that may not be obvious clinically. In addition to injury, MCL bursitis can occur and may be treated with needle aspiration and corticosteroid injection. This review article covers the anatomy and biomechanics of the MCL, its injury patterns and approach to management, and MCL bursitis.