What is a discoid meniscus?

A normal meniscus is a c-shaped cushion of cartilage that supports the knee joint. A discoid meniscus is shaped more like a disc and does not taper as much toward the center.  It can be a partial or a complete disc of tissue.

In some patients, a discoid meniscus can cause pain or decreased motion in their knee.   Some patients may experience a “popping” sensation.  The symptoms may start with a twisting injury to the knee or may start suddenly.

What causes discoid meniscus?

Approximately 1% of individuals are born with a discoid meniscus. Most of these abnormal menisci occur on the outer aspect of the knee.  Many people with a discoid meniscus are unaware they have it and don’t have any symptoms.

Is this a problem?

It can be. For those who have pain in the knee, limited range of motion, and catching or locking of the knee caused by the discoid meniscus or a tear in it, treatment may be recommended. If the discoid meniscus is not causing these symptoms, then it may not be a problem.

What are the treatment options?

If it is determined that the discoid meniscus is not the cause of the symptoms, the meniscus will be left alone and monitored.

If the cause of the symptoms is the discoid meniscus itself, arthroscopic surgery may be required to alleviate the pain and to allow the patient to fully straighten their knee. The surgeon will shave down the discoid meniscus in order to give it a more normal shape.  If there is an abnormal connection of the meniscus, that allows extra motion, it may need to be repaired.

What should I expect after surgery?

If the meniscus needs to be repaired due to an abnormal motion, the patient will need to use crutches for six weeks to allow healing.  Movement in the knee will be encouraged.  A return to normal activity should be expected in six to eight weeks.

If the meniscus has a good attachment and only needs to be re-shaped, then the patient can begin walking on the knee after surgery.   Crutches or a brace may needed for a short period to assist the patient with ambulation.  A return to normal activity should be expected in two weeks.

After surgery, the patient will have an Ace wrap around their knee, which should remain in place for 48 hours.  Placing ice on the knee for approximately 15 minutes every hour during the first two days is encouraged.

After two days, the Ace wrap can be removed but the clear dressing underneath should remain in place until the patient’s follow-up appointment.  Once the Ace wrap is removed, on the second day, showering is allowed though submerging the knee in a bath-tub should be avoided.

What should I expect long-term?

The discoid meniscus is an abnormal structure.  Though the surgeon can taper the shape of the meniscus to a more normal appearance, the tissue remains abnormal.  The remaining tissue remains more susceptible to future injury and may need additional surgery.