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St. Mary's Center for Orthopaedics

Discoid Meniscus

What is a Discoid Meniscus?

A discoid meniscus is an abnormally shaped meniscus in the knee. It is more prone to injury than a normally shaped meniscus.

Some people with discoid meniscus may go through their entire lives and never experience any problems. Most people, however, will have knee problems related to the discoid meniscus. Symptoms often begin during childhood.

The menicus is a wedge-shaped piece of cartilage that acts as a “shock absorber” between your femur (thighbone) and tibia (shinbone). The meniscus protects the articular cartilage that covers the ends of the bones and helps the knee to easily bend and straighten.

There are two menisci in the knee: the medial meniscus on the inside of the knee, and the lateral meniscus on the outside. Healthy menisci are shaped like crescent moons (in fact, “meniscus” comes from the Greek word for crescent).

The meniscofemoral ligament attaches the meniscus to the tibia bone so that it does not float around in the knee. This ligament also provides a blood supply to a small portion of the meniscus.

Types of Discoid Meniscus

There are three types of discoid menisci:

  • Incomplete – The meniscus is slightly thicker and wider than normal.
  • Complete – The meniscus completely covers the tibia.
  • Hypermobile Wrisberg – This occurs when the meniscofemoral ligament that attaches the meniscus to the tibia is absent. Without this ligament, even a fairly normally shaped meniscus can sometimes slip into the joint and cause pain, as well as locking and popping of the knee.

What Causes a Discoid Meniscus?

A discoid meniscus is a genetic abnormality. Most people with a discoid meniscus are unaware they have it and don’t have any symptoms.

What are the Symptoms of a Discoid Meniscus?

The most common symptoms of a discoid meniscus or torn discoid meniscus are:

  • Pain
  • Stiffness or swelling
  • Catching, popping, locking of the knee
  • Feeling that the knee is “giving way”
  • Inability to fully extend (straighten) the knee

How is a Discoid Meniscus Diagnosed?

A thorough medical history and physical exam can assist a trained physician in diagnosing a discoid meniscus. If a physician suspects a discoid meniscus, they will likely order an MRI to confirm the diagnosis and to determine the severity of the case.

What is the Treatment for a Discoid Meniscus?

If it is determined that the discoid meniscus is not the cause of the discomfort, the discoid meniscus will be left alone and the cause of the injury will be treated. However, if the root of the injury is the discoid meniscus itself, surgery may be required to alleviate the pain and to allow the patient to fully straighten the knee. The surgeon will shave down the discoid meniscus in order to give it a more normal shape.  In many cases, the most effective treatment is to remove the part of the discoid meniscus that is torn.  Some tears of the discoid meniscus can be repaired, rather than removed. In these cases, the surgeon will use stitches to sew the meniscus to the lining of the joint.

Recovery and Rehabilitation

It is important for patients to strictly adhere to the treatment plan set forth by the physician. After healing, it is typical to have a full return to activity, though a risk of recurrence is possible. The patient will need to continue to work on strengthening and technique in order to limit the possibility of further injury to the meniscus.

Most patients return to normal daily activities after arthroscopy for a discoid meniscus. However, if the meniscus was removed, there is a risk for continued pain and, potentially, early arthritis. Once the initial healing is complete, your doctor may prescribe physical therapy exercises to restore strength and mobility. These may be done at home or with a physical therapist. Surgeons sometimes recommend that patients avoid sports that overstress the knee with cutting type movements. These include soccer, tennis, basketball, and football.