Synovitis

Synovitis is the inflammation of the synovial membrane, the delicate lining that encloses joints, tendon sheaths, and bursae. This inflammation often leads to thickening of the synovium and accumulation of excess synovial fluid, producing joint swelling, pain, and reduced range of motion. Although it can affect any joint, larger joints such as the knee and smaller joints of the hands are commonly involved. Synovitis may occur as a primary condition or as part of another disease process.

Many etiologies can cause synovitis. Inflammatory and autoimmune diseases, such as rheumatoid arthritis and psoriatic arthritis, frequently involve the synovium. Crystal arthropathies, notably gout and pseudogout, can inflame the synovial lining. Septic arthritis represents infection within the joint and requires urgent treatment. Mechanical or overuse injuries, trauma, and repetitive motion can produce noninfectious synovitis. Tendon sheath synovitis (tenosynovitis) and bursae inflammation are related processes in nearby soft tissues.

Diagnosis relies on clinical assessment supported by imaging and laboratory tests. Ultrasound can detect synovial thickening and fluid, while MRI provides detailed visualization. Blood tests may reveal inflammatory markers (CRP, ESR) and disease-specific antibodies; synovial fluid analysis distinguishes inflammatory, crystalline, and septic processes by appearance, cell count, Gram stain, and cultures.

Treatment targets the underlying cause and symptom relief. Options include NSAIDs or acetaminophen for pain, rest and activity modification, and intra-articular corticosteroid injections. Antibiotics are essential for septic arthritis, and drainage or surgical intervention may be required. Early diagnosis and management reduce the risk of joint damage and improve outcomes.