Description of Discoid Meniscus
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).
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.