Arthritis Symmetric polyarthritis 2017-03-24T10:28:11Z Polyarthritis refers to a joint disease that involves at least five joints. One or more signs of inflammation, including pain, movement restriction, swelling, warmth, and redness, are seen in the joints involved. Polyarthritis is defined as symmetric if at least half of the joints involved are affected in a symmetric (i.e., both right and the left) fashion. In the event that pain is the only symptom, it is difficult to differentiate polyarthritis from the causes of polyarticular joint pain, such as fibromyalgia or osteoarthritis.