Medial Collateral Ligament of the Knee

Original Editor - Rebecca Wilson

Top Contributors - George Prudden, Kim Jackson, Lucinda hampton, 127.0.0.1, WikiSysop, Vidya Acharya, Rucha Gadgil and Saimat Lachinova   

Description

The medial collateral ligament (MCL) is a flat band of connective tissue that runs from the medial epicondyle of the femur to the medial condyle of the tibia and is one of four major ligaments that supports the knee. MCL injuries often occur in sports, being the most common ligamentous injury of the knee, and 60% of skiing knee injuries involve the MCL). 

NB The MCL is also known as the  tibial collateral ligament (see image)

The MCL

• Provides valgus stability to the knee joint. 
• Is a strong broad band found on the inner aspect of the knee joint and is the largest structure situated on the medial side.
• The most common ligament injury of the knee. 

This structure is divided into superficial and deep ligaments.

• The superficial ligament is also known as the tibiofemoral ligament
• The deep ligament is identified as the mid-third capsular ligament.

Attachments

1. The superficial medial collateral ligament (sMCL) has one femoral and two tibial attachments. 

• The femoral attachment is situated on the medial epicondyle.
• The proximal attachment 1. blends into semimembranosus tendon and 2. distal attachment is at the posteromedial crest of the tibia.

2. The Deep medial ligament (dMCL) is divided into two, the meniscofemoral and meniscotibial ligaments.

• The origin of the meniscofemoral comes from the femur just distal to the superficial medial collateral, inserting into the medial menisci.
• The meniscotibial ligament is thicker and shorter. It travels from the medial meniscus to the distal edge of the articular cartilage of the medial tibial plateau.

Function

The medial collateral ligament is recognised as being a primary static stabiliser of the knee and assists in passively stabilising the joint.

The superficial and deep ligaments each have a unique function, making the MCL the primary responder to valgus stress and a secondary restraint to rotational forces.

• The sMCL, specifically the proximal division, resists valgus forces through all degrees of knee flexion. The distal division of the sMCL helps stabilize external rotation of the knee at 30-degree flexion.
• The dMCL helps stabilize internal rotation of the knee from full extension through 90-degree flexion (assists the knee in rotational stability primarily in extension moving through into early flexion).. Despite the relationship of the dMCL with the medial meniscus, there is no influence of the MCL on the stability of the medial meniscus

Together, the MCL also helps guide the knee joint through its full range of motion when a tensile load is applied.

• With low load, the ligament is relatively compliant; with increasing load, the ligament responds with increasing stiffness until it is nearly linear. Beyond this, the MCL will continue to absorb energy until failure.

The MCL also prevents hyperextension of the joint and posterior translation of the tibia, secondary to the function of the posterior cruciate ligament (PCL). The posterior oblique ligament, a continuum of oblique fibers at the posterior aspect of the MCL, is responsible for this function.

The ligament also plays a role in joint position sense or proprioceptive feedback. When the MCL is stretched beyond its ability or exposed to an excessive load, it evokes neurological feedback signals that then generate a muscle contraction.

Blood Supply

Branches of the superior and inferior genicular arteries supply the MCL. The area near the bony insertions is more richly vascularized.

Nerves

The MCL is innervated by the medial articular nerve, a branch of the saphenous nerve.

• Innervation is greatest in the epiligament and near the insertions.
• The ligament can perceive pain and process proprioception through specialized sensory mechanoreceptors like Ruffini endings, Pacinian corpuscles, Golgi receptors, and bare nerve endings.
• Complete MCL tears will completely disrupt the pattern of innervation.

Clinical Relevance

The MCL is one of the most commonly injured ligaments of the knee.

• Valgus stress is the most common mechanism of injury.
• Injuries can be contact (a direct blow to the outer aspect of the lower thigh or upper leg) or non-contact (common in skiing). Contact injuries are usually more severe.

Injuries to the MCL can have detrimental effects to surrounding structures.

• It is recognised that either partial or complete ruptures in the ligament significantly increases the load on the ACL.
• Partial tears show that increases in ACL load were identified at 30 degree knee flexion and valgus load and internal torque.
• The medial meniscus is often also injured due to its relationship with the dMCL

Assessment

Assessment of the MCL is best within 20 to 30 minutes of injury before pain, swelling, and muscle spasms make examination difficult. The assessment includes palpation and a special test, the valgus stress test VST

1. Palpation

The anterior aspect of the ligament can be palpated moving vertically, roughly midway along the medial joint line. Focal tenderness indicates an MCL injury.

2. Special test

The VST assesses laxity of the MCL compared to the contralateral knee as a control. An increase in laxity and joint space usually distinguishes damage to the medical collateral ligament.

The patient should be positioned supine.

• Perform with the knee in approximately 30 degrees flexion rather than extension, ensuring isolated testing of the MCL (flexion helps to relax surrounding structures including the posterior capsule).
• Therapists position one hand on the lateral aspect of the joint line of the knee with the other hand on the medial aspect of the ankle.
• A valgus force is then applied, a positive result of the knee in this position would be an increase in joint space medially.

When assessing for an MCL injury, the examiner should carefully inspect surrounding structures. Suspicion of additional injury may require imaging.

Treatment

Treatment is often non-operative because the MCL has strong vascular support for healing. See Medial Collateral Ligament Injury.

See also

• Knee
• Anterior cruciate ligament
• Medial meniscus
• MCL injuries
• Pellegrini-Stieda syndrome
• Diagnostic imaging of the knee