MCL / PMC
Medial Collateral Ligament
Posteromedial Corner
Phone +971-2-4446600
Anatomy
The medial side of the knee has two important ligaments, joint capsule and several muscles to help control stability. The two ligaments are the medial collateral ligament (MCL) and the posterior oblique ligament (POL).
The most important function of the ligaments is to stabilize the knee in medial direction and with rotation, that is keeping your knee from giving away towards the other knee.
Injury
Valgus force, meaning the knee buckling in a medial direction, in combination with rotation is the most common way to get a medial or posteromedial injury to the knee. As an isolated injury, not combined with other ligament injuries, it is usually a partial injury that can heal well. However, it also commonly occurs in combination with ACL tears and requires larger forces to break, usually with a significant rotational injury, like a skiing accident or tackle during sports.
As with any ligament tears, the pain and swelling usually subsides, but the main remaining symptoms are instability, stiffness and medial tenderness to the knee, specifically medial buckling of the knee.
However, with a complete posteromedial corner injury, usually combined with other ligament injuries, the two ligaments, MCL and POL, are torn resulting in increased valgus laxity and rotation, leaving the knee with significant instability.
MRI of normal MCL
MRI of MCL tear
Evaluation
When the patient can explain what happened during the injury it helps a lot to understand the possible injuries to the knee. With an examination of the knee, further suspicion should arise for these injuries, but unfortunately it is not uncommon, especially with combined medial injury and for example an ACL tear, to understand the ACL injury but then miss or neglect the medial sided injury. With this in mind, it is important to always examine the entire knee and compare it to the healthy knee when an injury has occurred.
If there is any hesitation regarding medial sided injuries or combined injuries, x-rays and MRI are important to complement the examination with further information.
For chronic injuries stress-X-rays, meaning x-ray evaluation while putting pressure on the knee from different directions, is crucial in understanding the instability pattern.
MCL Stress X-rays
To the right: Valgus laxity during examination under anesthesia due to MCL tear
Treatment
After assessment, the instability is graded from 0-3.
When there is no instability, or possibly a minimal instability with an acute injury, this is treated with physiotherapy alone, graded 0-1, and defined as a sprain of the MCL. They typically heal very well with no future instability or need for further treatment after 6-8 weeks.
For the acute moderate instabilities, grade 2, a brace is used for 6 weeks and the physiotherapy program generally needed for up to 3-4 months.
When talking about the most severe injuries, the grade 3 injuries, with significant instability, it is important to evaluate the knee and MRI to define where the injury on the ligaments are. If the upper part, proximal, is injured, a conservative treatment plan is made with a brace and re-testing of the stability when the pain and swelling has settled down and the patient has regained proper motion in the knee. Some of these injuries need surgery to get proper stability, but some of them can heal with bracing and good physiotherapy. On the other hand, when the ligament tear is in the lower portion, distal, the chance of healing is lower and sometimes can even require acute surgery to re-attach the ligament to the bone (avulsion fixation).
For those injuries that need surgery, the stability pattern with extension and flexion (straightening and bending) of the knee is important to evaluate and plan the surgery. Usually, either only the MCL or both MCL and POL are reconstructed using your own hamstring tendons, but sometimes allograft tissue (donor tendons) can be used.
Chronic medial instabilities can rarely improve very much with non-operative treatment and is therefore more commonly treated with surgical reconstruction.
Image of posteromedial corner reconstruction of both MCL and POL
Rehabilitation
After surgical reconstruction of the medial side there is need to offload the knee, meaning you will be non-weightbearing or mildly partially weightbearing for the first 6 weeks and thereafter wean off the crutches. During this first phase of the rehabilitation you will still need physiotherapy to activate the muscles around the knee and work on your range of motion.
After about 8 weeks you can walk and drive a car again, and usually at 4-6 months you can progress back to running and thereafter sports.