From Carol & Richard Eustice,
Your Guide to Arthritis.
FREE Newsletter. Sign Up Now!

About.com Health's Disease and Condition content is reviewed by Kate Grossman, MD

Definition: Synovium is the smooth lining of a joint. A flexible joint is lined by a synovial membrane. Synovium produces synovial fluid (illustration), a clear substance that lubricates and nourishes the cartilage and bones inside the joint capsule.

In rheumatoid arthritis, the synovium becomes inflamed. Like many other rheumatic diseases, rheumatoid arthritis is an autoimmune disease, so-called because a person's immune system, which normally helps protect the body from infection and disease, attacks joint tissues for unknown reasons. White blood cells, the agents of the immune system, travel to the synovium and cause inflammation (synovitis), characterized by typical symptoms of rheumatoid arthritis such as:

warmth

redness

swelling

pain

During the inflammation process, the normally thin synovium becomes thick and makes the joint swollen and puffy to the touch.

As rheumatoid arthritis progresses, the inflamed synovium invades and destroys the cartilage and bone within the joint. (illustration) The surrounding muscles, ligaments, and tendons that support and stabilize the joint become weak and unable to work normally. These effects lead to the joint pain and joint damage often seen in rheumatoid arthritis patients.

Related Resources - Rheumatoid Arthritis

Rheumatoid Arthritis

Rheumatoid Arthritis Screening Quiz

Test Your Knowledge: Rheumatoid Arthritis

Guide To Rheumatoid Arthritis

Related Resources - Inflammation

Inflammation

Inflammation: The Battle Within

Test Your Knowledge: Inflammation

Pronunciation: SIN-O-VEE-UM

Also Known As: joint lining

Common Misspellings: sinovium

Examples: The synovium appeared to be inflamed.

_{Source: NIH Publication No. 04-4179}