What Is Synovitis?

From Symptoms to Treatment

Knee pain, conceptual computer artwork.
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Synovitis is the medical term for inflammation of the lining of a joint (ie., the synovium). Symptoms associated with synovitis include joint pain, joint swelling, redness, and warmth.

In healthy individuals, the cause of synovitis is usually overuse of a joint. Synovitis also is a primary characteristic of various types of inflammatory arthritis. With arthritis, the aforementioned symptoms are usually detectable during a physical examination.

Subclinical Synovitis

Subclinical synovitis is defined as inflammation of the lining of the joint that is not found during a physical examination. Subclinical synovitis can be detected using MRI (magnetic resonance imaging) but its significance is in question. According to rheumatologist Scott J. Zashin, M.D., "In my experience as a rheumatologist, patients with subclinical synovitis and normal measures of inflammation in the blood, such as a normal erythrocyte sedimentation rate or C-reactive protein (CRP), are unlikely to develop joint damage that is evident on basic x-rays, although I am not aware of any published studies on this subject."

While MRI is undeniably the best imaging method for soft tissue studies, it is expensive and time-consuming. Musculoskeletal ultrasound is gaining favor and has been recognized as cheaper and equally as effective as MRI for detecting synovitis.

The Significance of Active Synovitis

By the time symptoms of synovitis are visible or observable during physical examination, there is active inflammation already occurring at the affected joint.

Active synovitis can lead to permanent joint damage. That is precisely the concern when synovitis is detected and exactly why early diagnosis and treatment of arthritis is often emphasized.

Synovitis can not only damage a joint, but it can affect surrounding structures, such as the tendons. A severely damaged joint can become deformed or even fuse together, making normal mobility and function difficult or impossible.

What Precedes Symptomatic Synovitis?

During the first few weeks of symptomatic rheumatoid arthritis, there can occasionally be fewer white blood cells or tissue edema than expected with inflammation, but biopsy often reveals a cellular appearance characteristic of advanced disease. Patients with "early rheumatoid arthritis" may actually have a disease process underway which precedes the onset of symptoms. Autoantibodies (antibodies against the body's own tissues) are thought to be produced in patients with rheumatoid arthritis years before clinical symptoms appear. This suggests a preclinical phase which may occur before symptomatic synovitis. 

Once synovitis has been diagnosed as the cause of joint pain, swelling, redness, or warmth, the cause of the joint inflammation needs to be determined. With a proper diagnosis, appropriate treatment can begin. Nonsteroidal anti-inflammatory drugs (NSAIDs) are typically prescribed immediately to dampen down inflammation. In rheumatoid arthritis, disease-modifying anti-rheumatic drugs (DMARDs) and biologic drugs are typically added as part of the treatment regimen to bring synovitis under control, prevent joint damage, and slow disease progression.



Kelley's Textbook of Rheumatology. Ninth edition. Elsevier. Etiology and Pathogenesis of Rheumatoid Arthritis. Chapter 69.

Synovitis. Hospital for Special Surgery. Accessed 01/11/16.

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