Gull-wing appearance (phalanges)

The gull-wing appearance, also known as seagull erosions or sawtooth appearance, is classically seen in erosive osteoarthritis, typically on posteroanterior radiographs of the hands, although has also been reported in psoriatic and rheumatoid arthritis. These erosions more commonly occur at the distal interphalangeal joint than the proximal interphalangeal joint.

Radiographic features

The combination of cartilage space loss, central subchondral erosions, and marginal osteophyte proliferation result in this appearance. At the distal joint, there are paracentral erosions, and at the proximal joint there is a central erosion - this pattern is thought to occur where the articular cartilage is at its thinnest .