Synovitis is the inflammation of a synovial (joint-lining) membrane, usually painful, particularly on motion, and characterized by swelling, due to effusion (fluid collection) in a synovial sac.
Synovial fluid is a transparent, viscid fluid secreted by the synovial membrane and found in joint cavities, bursae, and tendon sheaths.
Rheumatoid arthritis involves synovitis. In rheumatoid arthritis, the synovial membrane lining the joint becomes inflamed. The cells in the membrane divide and grow and inflammatory cells come into the joint from other parts of the body.
Because of the mass of inflammatory cells in rheumatoid arthritis, the joint appears swollen and feels puffy or boggy to the touch. The increased blood flow that is a feature of the inflammation makes the joint warm. The cells release enzymes into the joint space which causes further pain and irritation. If the process continues for years, the enzymes may gradually digest the cartilage and bone of the joint leading to chronic pain and degenerative changes.
In addition to the clinical presentation (warm, red, and swollen joints), the diagnosis may be helped by Synovial Fluid Analysis. This is a test that examines the lubricating fluid secreted by synovial membranes. The test is useful in the diagnosis of some types of arthritis (primarily those caused by infection, gout, or pseudogout).
The test takes about half an hour and usually is done in a physician's office or hospital. No special preparations are necessary. The skin over the joint is cleaned with an antiseptic. Usually, a local anesthetic is injected. Using a thin needle, the physician will withdraw a sample of fluid for analysis, including culture of the fluid if infection is a possible diagnosis, and examination for crystals to diagnose gout or pseudogout.
If needed, medication (usually a corticosteroid preparation) can be injected into the joint space through this needle after the specimen is taken.
Synovitis is treated with anti-inflammatory drugs ranging from aspirin to ibuprofen to corticosteroids. Specific treatment is based upon both the presumed cause of the synovitis and the particular patient's response and level of tolerance of any particular medication.