Active Synovitis Versus Subclinical Synovitis

Diagnosis and Treatments of Different Forms of Synovitis

Synovitis is inflammation of the synovium, which is the lining of a joint. Symptoms associated with synovitis include joint pain, joint swelling, redness, and warmth.

In the absence of inflammatory disease, synovitis is usually caused by overuse of a joint. Synovitis is also a feature of various types of inflammatory arthritis. With inflammatory arthritis, signs of synovitis are usually detectable during a physical examination.

Illustration of knee joint inflammation
Witthaya Prasongsin / Getty Images

Subclinical Synovitis

Subclinical synovitis is inflammation of the lining of the joint that is not detectable with a physical examination. Subclinical synovitis can be identified using magnetic resonance imaging (MRI) or ultrasound. This condition is not considered important as a primary diagnosis, but identifying it can help in differentiating osteoarthritis/fibromyalgia from inflammatory arthritis and with assessing disease activity.

According to rheumatologist Scott J. Zashin, MD, "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 considered the best imaging method for assessing soft tissue, it is expensive and time-consuming. Musculoskeletal ultrasound is gaining favor and has been recognized as cheaper and equally as effective as an MRI for detecting synovitis.

Active Synovitis

By the time symptoms of synovitis are visible or observable during a physical examination, active inflammation is 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 are emphasized.

Synovitis can damage a joint and its surrounding structures, such as the tendons. A severely damaged joint may become deformed or its structures can fuse together, impairing normal mobility and function.

Symptomatic Synovitis

Synovitis and Rheumatoid Arthritis

Early in the course of symptomatic rheumatoid arthritis, you might not have elevated white blood cells or tissue edema. But a biopsy often reveals a cellular appearance that's characteristic of this disease.

People with early rheumatoid arthritis may actually have an ongoing disease process that precedes the onset of symptoms. Autoantibodies (antibodies against the body's own tissues) are thought to be produced in people with rheumatoid arthritis years before clinical symptoms appear. This suggests a pre-clinical phase which may occur before symptomatic synovitis develops. 

Synovitis and Monoarthritis

Once synovitis is identified, the cause of joint inflammation needs to be determined. The presence of synovitis limits the differential diagnosis to inflammatory types of arthritis, infectious arthritis, and systemic rheumatic diseases.

In its very early stages, rheumatoid arthritis may begin as monoarthritis (arthritis symptoms affecting one joint). If you have monoarthritis, your physical examination will establish the presence or absence of joint effusion or synovitis.

As it progresses, rheumatoid arthritis typically becomes symmetrical polyarthritis, meaning that multiple joints are involved approximately equally on both sides of the body. 

Treating Symptomatic Synovitis

With a proper diagnosis, appropriate treatment can begin. In rheumatoid arthritis, disease-modifying anti-rheumatic drugs (DMARDs) and biologic drugs are typically used to bring synovitis under control, to prevent joint damage, and to slow disease progression.

DMARDs are usually prescribed right away, but they are slow acting. Therefore, treatment with non-steroidal anti-inflammatories (NSAIDs) or low dose steroids can help dampen down inflammation.

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