The meniscus is a wedge-shaped piece of cartilage that sits in between the bones of the knee and acts as a cushion to protect the bones during movement. Each knee has two menisci.
Normal menisci are shaped like crescent moons (in fact, "meniscus" comes from the Greek word for crescent). A discoid meniscus is thicker than normal, and often oval or disc-shaped. It is more prone to injury than a normally shaped meniscus. Approximately 1% of individuals are born with a discoid meniscus. Discoid menisci is congenital, frequently bilateral.
Some people with discoid meniscus may go through their entire lives and never experience any problems. Many people, however, will have knee problems related to the discoid meniscus. Symptoms often begin during childhood.
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 does not require treatment.
If the cause of the symptoms is the discoid meniscus, arthroscopic surgery may be required to alleviate the pain and to allow the patient to fully straighten his knee. During surgery the meniscus needs to be re-shaped (this called saucerization) to convert its shape to the normal crescent shape. A return to normal activity is usually expected in two weeks.