Causes of Synovitis
Synovitis is a defining characteristic of rheumatoid arthritis, an autoimmune disease that causes chronic inflammation of the joints. In this condition, cells in the inflamed membrane attract other inflammatory cells from all around the body to induce an inflammatory process causing joint pain.

Synovitis joint pain can be seen in other illnesses such as juvenile arthritis, lupus, psoriatic arthritis, rheumatic fever, tuberculosis, injury, or gout. However, there are some cases where the cause of synovitis is not known, with the affected individual possibly sustaining a minor injury or not recalling having an injury at all, yet the signs of synovitis inflammatory condition are appreciated.