[no-glossary]Synovitis[/no-glossary] is associated with certain diseases that raise the risk of inflammation. They include:

• rheumatoid arthritis
• lupus, a chronic inflammatory disease that can affect parts of the body including the joints
• gout, a buildup of uric acid crystals in the joints of the body, causing inflammation, swelling, and pain

Synovitis can also be caused by injury to the shoulder joints, which respond with inflammation. Sometimes, the cause is unknown.