Meniscus Pathology

Discoid lateral meniscus

What is it ?

Lateral discoid meniscus is present in 1% of the population in Europe (10% in Asia), which means that instaed of a C-shape, the lateral meniscus has a O shape, and then more at risk of tear. Patients are usually asymptomatic as long as the lateral discoid meniscus is intact; it will become painful when torn or unstable, which happens more often in the youth. Usually, the patient is informed that he has a lateral discoid meniscus because it is seen on the MRI, otherwise some people live all their life without being aware of it.

Clinical presentation

A torn lateral discoid meniscus gives lateral knee pain, sometimes swelling, lockings or clics in the joint.

When to consult a specialist?

In case of persisting pain on the lateral side of the knee, swelling, lockings or clics.

Non surgical treatment

If a lateral discoid meniscus is intact and asymptomatic, it must be treated conservatively. However, if torn, there is few chances that a conservative treatment will cure the patient.

Surgical treatment

Most of the time, a lateral discoid meniscus gets torn centrally: in that case, the torn central part is removed (a minima) to give the meniscus a C-shape back (it is called a “meniscoplasty”). Sometimes, the discoid meniscus is torn at its periphery, at the menisco-capsular junction, which creates instability and lockings of the joint: in that case, menisco-capsular sutures will reduce and stabilise it, and it may be associated to a meniscoplasty if necessary.

Postoperative follow-up

The post-oprative rehabilitation protocol has to be progressive: in case of meniscoplasty, walking without crutches will be allowed after 10 days but jumps/running/pivoting activities should be avoided during a month to avoid a “chondrolysis” (see risks and complications”). In case of menisco-capsular sutures, walking with crutches for 4 to 6 weeks and limiting the knee flexion at 90° will allow the healing.

Risks and complications

The most important risk in case of meniscoplasty is the chondrolysis, which is a fast cartilage degeneration of the lateral compartment of the knee. Clinically it should be suspected in case of persistant knee swelling and pain. An MRI can show a swollen knee and a thinning of the lateral femorotibial cartilage. A knee arthroscopy is the best diagnostic evaluation and the appropriate treatment to wash out the loose chondral bodies and the inflammatory factors. The patient should walk with crutches to lower the mechanical constrains on this damaged cartilage and enhance its healing.

In case of lateral discoid meniscus repair, the risks and complications are the same as any other meniscal repair.