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Definition
By Gregory R. Waryasz, MD
The medial collateral ligament (MCL) of the musculoskeletal system is characterized by being an intrinsic (capsular) band. The superficial component is referred to as the tibial collateral ligament and the deep component is referred to as the medial capsular ligament.
It is part of the knee joint. It consists of fibrous dense regular connective tissue of collagen fibers.
Its unique structural feature is that it is made up of two layers; superficial and deep. The ligament is a strong and flat band.
The superficial medial collateral ligament is the middle layer of the medial compartment of the knee. The proximal attachment is the posterior medial femoral condyle. The distal attachment is the tibial metaphysis about 4-5 cm distal to the joint line and beneath the pes anserinus. The superficial medial collateral ligament can be further differentiated into the anterior and posterior portion. Fibers from the posterior portion help to form the posterior oblique ligament.
The deep medial collateral ligament is the deep layer of the meidal compartment. It may be separated from the superficial medial collateral ligament by a bursa. It originates from the femur and blends with the superficial fibers distally. It attaches to the medial meniscus.
The blood supply to the medial collateral ligament is from the superomedial and inferomedial genicular arteries.
The medial collateral ligament as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.
The function of the medial collateral ligament provides a primary restraint to valgus forces. At 25 degrees of flexion, the MCL provides 78% against valgus stress. At 5 degrees of flexion, the MCL contributes 57% against a valgus stress. The anterior portion of the superficial medial collateral ligament tightens with knee flexion between 70 and 105 degrees. The posterior superifical medial collateral ligament tightens with extension. The deep medial collateral ligament does not provide much resistance to valgus forces.
Common diseases include ligament tears and sprains. It can be injured in combination with other structures in the knee.
The medial collateral ligament can tear and/or sprain. The clinical findings may be subtle, but there also may be a significant opening of the medial compartment when a valgus stress is applied. Tenderness may also be present over the medial collateral ligament.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, and MRI. The Pellegrini-Stieda phenomenon is calcification at the MCL origin.
It is usually treated with physical therapy, immobilization, and NSAIDs. Combined injuries with anterior cruciate ligament tears or meniscal tears usually require surgery. If there is an avulsion of the femoral origin, surgery may be required to fix the ligament.
References
Elstrom J, Virkus W, Pankovich (eds), Handbook of Fractures (3rd edition), McGraw Hill, New York, NY, 2006.
Koval K, Zuckerman J (eds), Handbook of Fractures (3rd edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Wheeless’s Textbook of Orthopaedics: Medial Collateral Ligament (http://www.wheelessonline.com/ortho/medial_collateral_ligament)