IL1A and Arthritis: IL-1 plays a central role in the degradation of articular cartilage and in the pathogenesis of osteoarthritis (OA), post-traumatic osteoarthritis (PTOA) and rheumatoid arthritis (RA) (1–5), which are common forms of ‘arthritis’, an umbrella term for a large number of disease processes that lead to whole joint damage, resulting in pain and disability.