"Hook" erosions in Jaccoud's arthropathy

Jaccoud's aethropathy is a non-erosive deforming arthritis seen in rheumatic fever, systemic lupus crythematosis and ankylosing spondylitis. "Hook" erosions may occur on the radial palmar aspect of the metacarpal heads and can be differentiated from the marginal erosions of rheumatoid arthritis.