What is synovitis?

Your shoulder joints are held together by a " capsule " of tissues and ligaments. The innermost tissue of the capsule is a membrane called the synovium (def.).

The synovial membrane secretes a clear fluid called synovial fluid that lubricates joint surfaces and provides the cartilage (def.) with nutrients. Sometimes this capsule becomes inflamed. The result is the painful condition called synovitis.

Here's what happens when synovitis occurs:

  • Disease (such as rheumatoid arthritis) or injury causes white blood cells to move from your blood stream into your synovium
  • The synovium cells grow and divide abnormally. Fluid collects as the synovium becomes thickened and inflamed
  • The synovial cells release enzymes
  • The enzymes may eventually destroy joint cartilage and bone, as well as surrounding muscles, ligaments, and tendons
What causes synovitis? Who's at risk?

Synovitis is associated with certain diseases that raise the risk of inflammation. They include:

  • rheumatoid arthritis
  • lupus, a chronic inflammatory disease that can affect parts of the body including the joints
  • gout, a buildup of uric acid crystals in the joints of the body, causing inflammation, swelling, and pain

Synovitis can also be caused by injury to the shoulder joints, which respond with inflammation. Sometimes, the cause is unknown.

How is synovitis diagnosed and treated?

Warm, swollen shoulder joints can be an indicator of synovitis. Your shoulder may be painful both at rest and with movement. If synovitis is suspected, your physician may withdraw a sample of your synovial fluid from the shoulder joint to send to a laboratory to test for infection or the crystals that indicate gout.

Treatment depends on the cause of the synovitis. It is likely to include anti-inflammatory medications, oral steroids, or cortisone steroid injections.

In some cases, your physician may recommend surgical removal of the inflamed synovium. If appropriate, the surgery may be the minimally invasive surgery called arthroscopic surgery.

What can I expect long-term?

Conservative treatment with anti-inflammatories may help symptoms and give your shoulder a chance to heal. Individuals with long-lasting synovitis, including individuals with rheumatoid arthritis, may need further care.