Polyarthritis is defined as inflammation affecting five or more joints simultaneously, which can result from various underlying conditions such as rheumatoid arthritis, psoriatic arthritis, or viral infections. It is clinically significant as it can lead to joint damage, functional impairment, and decreased quality of life if not diagnosed and managed promptly. A key association is rheumatoid arthritis, which can cause systemic complications, including cardiovascular disease and osteoporosis.