Synovitis Definition

Inflammation of joint tissue called synovium is called synovitis. This condition may develop as the result of repetitive joint movement, an injury, infection, or arthritis. Synovitis may cause joint pain, tenderness, swelling, stiffness, and other symptoms.

Another term for synovium is synovial membrane. Synovium is a type of connective tissue that:

  • Is very thin, typically about the width of a human hair
  • Lines most of the body’s joints (synovial joints) and many structures related to joints, such as bursae and tendons
  • Produces a thick, slippery fluid called synovial fluid, which is essential to joint health

Synovial fluid reduces friction between tissues during joint movement and helps provide a cushion between joints’ bones. It also supplies nutrients to joints’ cartilage.

Synovitis changes synovium and its ability to help keep joints healthy. When inflamed, the synovium may:

  • Grow thicker
  • Produce too much synovial fluid
  • Produce synovial fluid that is less thick, slippery, and nutrient-rich
  • Release chemicals called cytokines that contribute to pain and joint tissue degeneration

Synovitis may be temporary or chronic. Scientists continue to learn about synovitis and its role in joint health and disease.

Many types of arthritis are associated with synovitis, including but not limited to:

  • Osteoarthritis1
  • Rheumatoid arthritis
  • Psoriatic arthritis
  • Axial spondyloarthritis
  • Systemic Lupus Erythematosus (SLE)
  • Gout

In rheumatoid arthritis, the synovium may thicken and grow so much that it develops into a type of tissue called pannus.

See What Is Pannus?

Several treatments can help reduce the inflammation associated with synovitis. These treatments include but are not limited to resting the affected joint, applying a cold compress, taking anti-inflammatory medication, and participating in physical or occupational therapy.

When synovitis is related to a body-wide inflammatory disease, such as RA, then the underlying condition must be treated to relieve symptoms.


  • 1.Mathiessen A, Conaghan PG. Synovitis in osteoarthritis: current understanding with therapeutic implications. Arthritis Res Ther. 2017;19(1):18. Published 2017 Feb 2. doi: 10.1186/s13075-017-1229-9
  • 2.Abrar DB, Schleich C, Brinks R, et al. Differentiating rheumatoid and psoriatic arthritis: a systematic analysis of high-resolution magnetic resonance imaging features-preliminary findings. Skeletal Radiol. 2021;50(3):531-541. doi:10.1007/s00256-020-03588-5
  • 3.Hmamouchi I, Bahiri R, Srifi N, Aktaou S, Abouqal R, Hajjaj-hassouni N. A comparison of ultrasound and clinical examination in the detection of flexor tenosynovitis in early arthritis. BMC Musculoskelet Disord. 2011;12:91.