Anatomy
The MCL has three portions
- Superficial MCL, a delta shaped ligament that extends from the medial femoral epicondyle to 3-4 cm below the medial joint line beneath the pes anserinus tendons
- Deep MCL, a thickening of the medial capsule, is divided in the menisco-femoral and menisco-tibial ligaments, these portion is firmly attached to the medial meniscus
- Posterior oblique ligament, the superficial and deep portions of the MCL blend together in the posteromedial portion of the knee
Biomechanics
The MCL is the primary restraint to the valgus (medial opening) of the knee at extension as well as 30° of flexion.
We can divide the MCL as an anterior and a posterior band, the anterior tightens in flexion and the posterior in extension.
At 25° of flexion the superficial MCL affords 78% of the restraint to the abduction moment.
As the knee extends the oblique posterior ligament becomes taut and provides increased stability.
The isolated sectioning of the MCL has little effect on the anterior tibial translation.
Mechanism of Injury
The isolated injury is the result of a valgus force.
MCL injuries are frequent in contact sports such as football or rugby in which there are frequent blows to the external side of the knee.