Erosive osteoarthritis (EOA) is a peculiar form of osteoarthritis, characterized by inflammatory destructive changes (erosions) in the interphalangeal joints, with relative sparing of the metacarpophalangeal joints, and frequent involvement of the trapeziometacarpal joint. Linear periosteal bone apposition is also commonly reported. In EOA, erosions tend to occur exclusively in the subchondral cortex of joints, causing in DIP joints a typical "gull wings" configuration of bones of distal phalanges, whereas in psoriatic arthritis (PA) and in rheumatoid arthritis (RA) the "bare areas" are primarily affected. However, such "gull wings" erosions are nonspecific, and may be observed in the late stage of PA in the IP joints, or RA in the PIP joints.