Erosive osteoarthritis.

Erosive osteoarthritis (EOA) is a progressive disorder affecting the interphalangeal joints of the hands. Severe synovitis is superimposed on the typical changes seen in conventional interphalangeal osteoarthritis (OA), which includes formation of Heberden's and Bouchard's nodes. Imaging studies show a combination of bony proliferation (osteophytosis), periosteal reaction, and articular erosions, which assume "gull-wing" configuration. Differential diagnosis includes classic "degenerative" OA, rheumatoid arthritis, and psoriatic arthritis.