The menisci of the knee joint are made of tough, fibrous cartilage that conform to the surfaces of the bones upon which they rest. One meniscus is on the inside of the knee (known as the medial meniscus), and the other rests on the outside of the knee (known as the lateral meniscus).

Description of Discoid Meniscus

A normal appearing meniscus resembles a C-shape appearance. In a meniscus that shows an abnormality, once condition that may be diagnosed is a discoid meniscus. A discoid meniscus is a meniscus that is shaped like a pancake, instead of exhibiting the normally appearing C-shape. Thus, the central area of this “pancake” is much thinner and has a higher risk of tearing.

The incidence of a discoid meniscus, which almost always involves the lateral meniscus, is less than 1% in North America. In some Asian countries, it approaches 5-6% of the population. Because the central portion of the discoid meniscus is thinner, it is at a higher risk of tearing.

Symptoms of Discoid Meniscus

• Audible click or grind on the lateral aspect – specifically for young active adults
• Lateral joint pain

The usual diagnosis of a discoid lateral meniscus is found on an MRI scan. In some cases, the lateral joint space maybe be wider and the bones may be flatter, which may suggest that there is a lateral meniscus present on the plain X-rays.

Treatment for Discoid Meniscus

Typically, treatment for a discoid lateral meniscus is to resect the torn and unrepairable portion of the meniscus and try to reshape (also called saucerize) the remaining meniscus to have it function similar to a normal meniscus. In some instances, the whole meniscus may tear and be degenerative, and it is not possible to saucerize it back to a normal type shaped meniscus. In some rare circumstances, a very thick discoid meniscus may tear close to the edge, where there is still a blood supply from the joint lining, and a repair would be indicated in these circumstances.

Post-Op

Patients who have a discoid lateral meniscus excised have to be followed closely to make sure that they do not have the development of arthritis. It is recommended that they report back to their physicians for X-rays on a yearly basis, for at least the first few years after the meniscus is trimmed, and also to report back if there are any problems with pain or swelling with activities. Ultimately, young patients who need to have a discoid lateral meniscus completely resected may also need a lateral meniscal transplantation.

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