The Medial Collateral Ligament or MCL is a long, broad, flat ligament on the inside of the knee. It consists of a superficial portion and a deep portion which is attached to the medial meniscus via the coronary ligaments. The deep portion is also described as having menisco-femoral and menisco-tibial portions. An additional important restraint, the posterior oblique ligament runs down behind the MCL in a divergent manner.
The MCL helps to resist a valgus stress on the knee i.e it prevents the leg from moving outwards.
Injuries to the MCL can be graded both clinically and on MRI scans.
Clinically, a Grade I tear is characterized by pain on stressing the ligament but no additional opening. A Grade II tear has some additional opening on stressing but a solid endpoint feel i.e it represents a ligament that is damaged but has some fibres left intact. A grade III tear opens up and does not have an endpoint and represents a complete tear.
A grade I tear can be rehabilitated quite quickly, usually without a brace. A grade II tear will usually require a brace for support and requires a more prolonged period of rest and some restriction of motion.
Some controversy exists with regard to grade III tears and there are advocates of conservative treatment and surgery. This should be discussed on an individual patient by patient basis and is dependent on the age of the patient, their sporting demands and any associated ligament injuries.
Chronic injuries that have failed to heal and that present with persistent instability will require reconstruction, in a similar manner to ACL surgery. It is not possible to fix or tighten the torn ligament and instead, a new ligament is fashioned using a graft, usually some of the hamstrings tendons.
An incision is made down along the inside of the knee. If the hamstrings are being used as a graft, they are harvested at this point.
The anatomy of the inside of the knee is then carefully delineated to allow accurate identification of the necessary landmarks. On the femoral side this includes the medial epicondyle, the adductor tubercle and the gastrocnemius tubercle. On the tibial side, the insertion of the MCL and the posterior oblique ligament (POL) are identified.
Guidewires are placed at the proposed drill holes and the knee cycled through a range of motion to ensure that the grafts will be under almost equal tension throughout the arc. When the graft length does not change from flexion to extension, it is called Isometric.
Drill holes are then made at the 4 points and the grafts pulled through, tensioned and secured with special screws.
Once again a free range of movement of the knee is confirmed and it is carefully checked for side to side stability.
The wound is then closed in layers and dressings and a brace applied.
A special brace is required after surgery to give additional support to the knee as the graft heals. The amount of movement allowed will be determined at the time of surgery and slowly increased over the next 6 weeks. During this time, you will also need to protect the leg by using crutches and limiting the weight through the affected leg.
Recovery from an MCL reconstruction is a more prolonged process than with for example, an ACL. Stiffness is common and requires a significant amount of physiotherapy to help combat.
A return to sports is also much less predictable than with an ACL and will also depend on whether it was an isolated injury or part of a multi-ligament injury.
Compiled  October 2015
Review date: March 2016