Angels outfielder Cameron Maybin, sustained a Grade 1 right knee MCL sprain in a stolen base attempt on Tuesday. Also on Tuesday, Stephen Vogt, Brewers backup catcher, sprained his left MCL in a collision at the plate with Pirates pitcher Chad Kuhl. Kuhl remained in the game. The Grade of Vogt’s injury was not reported.
Some MCL Anatomy
A Medial Collateral Ligament, or MCL, is a ligament that stabilizes the inner (medial), aspect of joints such as at the knee and elbow. At the elbow, it is the ligament that is reconstructed when pitchers undergo Tommy John surgery. It is a fibrous band of tissue and – in the case of the MCL at the knee – it has both a superficial and deeper layer, each of which has different attachments. For more detail on the medial knee and origins and insertions of the ligament take a look here, or here.
The superficial MCL serves as the primary restraint to check against forces to the outer knee that would result in the knee collapsing inward. This is known as a valgus stress. The superficial portion of the MCL has both anterior (front) and posterior (rear) fibers and the degree to which they are effective in this role depends in large part on the position of the knee when the stress occurs. When the knee is almost extended, the ligament contributes somewhat less to the stability of the joint. Therefore, testing for the integrity of the MCL is done with the knee flexed to 30 degrees, an angle at which the ligament is most effectively isolated.
The deep layer of the MCL is often separated from its superficial counterpart by a bursa, which allows for a greater mechanical advantage and smoother gliding of tissues. A point of note with regards to the deeper layer of the MCL is its attachments to the meniscus both from the femur above and the tibia below (it also inserts directly into the top of the tibia at the tibial plateau). Because of its meniscal attachments, MCL injury can result in meniscal injury as well. Though the deeper layer does not contribute much as a restraint against valgus stress, it does serve as a secondary check to anterior translation of the tibia (which would result in knee hyperextension). The Anterior Cruciate Ligament (ACL) serves as the primary restraint to this motion. The relationship between the two ligaments is the reason that ACL injuries are often accompanied by those to the MCL.
Diagnosis and Treatment
Ligament sprains are graded from Grade 1 – which is a mild tweak causing less damage – to a Grade 3, or complete rupture. Time lost to competition depends on the severity of the injury, the specific location of the tear and the individualized nature of the healing process. Pain can be very localized or more diffuse depending on where the tear occurs. MCL tears at the attachment to the femur can result in a portion of the bone being avulsed, while tears more central to the ligament can cause significant soft tissue damage. Tears at or near the tibial attachment may cause pain to run down the shin and it is also possible to experience an MCL tear deep to the pes anserinus, a site of attachment of several muscles/tendons below the knee at the medial aspect of the tibia.
MRI can be helpful in identifying the location of the tear and the degree of damage. Treatment is generally non-operative with a healing response time for significant tears of six weeks. However, because remodeling of the scar tissue involved in the healing process can take up to a year, the tensile strength of the tissues can be compromised during that extended time. Interestingly, studies have noted that even though mature scar tissue has only 60% of the strength of a normal MCL, the fact that there is a proliferation of this tissue compensates sufficiently so that “the ultimate load to failure is unchanged”.
Surgical intervention may be indicated when a significant gap occurs in the MCL at the area of a tear or when a portion of bone is avulsed.