A discoid lateral meniscus is an abnormally shaped meniscus within the knee joint. The meniscus is a C-shaped wedge of cartilage that helps support and cushion the knee joint. In each knee there are two menisci, one on the inside (medial) and one on the outside (lateral) of the knee joint. In some people the lateral meniscus is shaped more like a solid disc rather than the normal C-shape.
Most people with a discoid meniscus never know they have an abnormality. It is estimated that between 3-5% of people have a discoid lateral meniscus. Most people live normal, active lives with a discoid meniscus--even high performance athletes. Therefore, if your doctor finds that you have a discoid meniscus, but it is not the causing symptoms, it should be left alone.
The two most common reasons people find they have a discoid meniscus are that they have an MRI that shows the abnormality, or they are having an arthroscopic knee surgery and are found at that time to have the discoid meniscus. Again, in both of these scenarios, the discoid lateral meniscus is best left alone.
Symptoms of A Problematic Discoid Menicus
In some people, the discoid meniscus can cause problems, usually a popping sensation with pain over the outside part of the knee joint. This is why some people use the phrase 'popping knee syndrome' when talking about a discoid meniscus. Signs of a discoid meniscus can include:
- Popping of the knee
- Knee swelling
- Pain along the outer side of the knee
- Pain with squatting/kneeling
Treatment of a Discoid Meniscus
If patients are found to have a discoid meniscus, but it is not causing symptoms, no treatment should be performed.
If these simple treatments do not relieve the symptoms, patients may choose arthroscopic surgery for the discoid meniscus. If the discoid meniscus is torn, the torn portion can be removed. In addition, the discoid meniscus can be surgically shaped into a normal appearing meniscus.
Jordan MR. "Lateral Meniscal Variants: Evaluation and Treatment" J Am Acad Orthop Surg July 1996 ; 4:191-200.