Medial Collateral Ligament (MCL) Injuries of the Knee

Overview of Medial Collateral Ligament Injuries

The medial collateral ligament, commonly referred to as the MCL, is a ligament located along the inner side of the knee. The MCL stretches from the thighbone (femur) to the shinbone (tibia) and helps to stabilize the inner (or medial) part of the knee. While several other ligaments and tendons, such as the hamstring tendons, provide additional support, the MCL is the most important structure that prevents the inner part of the knee from “gapping open” when the tibia bone is pulled outward (laterally).

The medial collateral ligament is commonly injured in soccer players as well as skiers and football players. Most injuries occur during a sliding tackle when the knee is subjected to a force (known as valgus force) that causes the tibia to bend outwards relative to the femur. An example of this is when an opposing player forcefully strikes the inside of one’s lower leg and forces it out during a slide tackle. During these episodes, the MCL can be injured by itself (isolated) or can be injured with the anterior cruciate ligament (ACL) and/or the medial meniscus, which is directly connected to the MCL. 

Diagnosis of Medial Collateral Ligament Injuries

When the medial collateral ligament is injured, most experience pain along the inner knee, and some can actually describe feeling or hearing a “pop.” For the first few days after the injury, the inner part of the knee can appear swollen and “black and blue” (ecchymotic) and is almost always tender to the touch. Unlike the ACL, the MCL is not located within the knee joint, and therefore swelling within the knee joint may herald an associated injury to the ACL and/or meniscus.

A physician can usually diagnose medial collateral ligament injuries based solely on history and physical examination. Therefore, an x-ray and MRI are not always necessary. An x-ray of the knee should be considered, however, in an adolescent with this injury, because a fracture through the growth plate at end of the femur can occur. MRI is generally reserved for severe injuries in which surgery is planned or in cases of suspected injury to the ACL and/or meniscus.

Treatment of the Medial Collateral Ligament

Treatment depends upon the injury grade, which is determined by the findings on physical examination (see table below). The vast majority of MCL injuries can heal without surgery.


Grade Injury Physical Exam
I Stretching of the MCL  Tender but no instability
II Partial tearing of the MCL Tender and mild instability
III Complete tearing of the MCL Tender and considerable instability

Table 1: Grading of medial collateral ligament injuries

Rest and Bracing: In order to allow healing, the knee should be rested for several weeks. Frequent application of ice and a compressive dressing help to limit swelling in the first few days following the injury. Prior to return to play, the knee should be re-examined to make sure that ligament has healed adequately. A special brace can be used to provide additional support when the player returns to sport.

Surgery: Surgery is reserved for a medial collateral ligament that fails to heal and restore stability to the inner knee even after a period of rest. Several options are available to surgically treat this injury, including repair or reconstruction of the ligament. If the ligament is reconstructed, either the patient’s own tissue or cadaveric tissue is used. The type of surgery and tissue used are based upon the injury as well as surgeon/patient preference.

Rehabilitation following the surgery is quite extensive and at least six months is often necessary prior to consideration of return to play.


Robert A. Gallo, MD
Fellow, Sports Medicine Service
Hospital for Special Surgery

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