Twelve patients, 11 women and one man, aged 66–83, with a distinctive type of destructive arthropathy are described. The principal joints affected were the shoulders (ten) and knees (seven). Clinical features included pain on use, large cool effusions, instability and rapid progression. Radiographs showed attrition of bone and cartilage with a paucity of reparative changes. Synovial fluids were viscous, with low cell counts, and stained positively for the presence of apatite-containing particles. Extensive calcific material was seen in the synovium of the four patients biopsied, and on the radiographs in seven. Most patients had some associated or preceding joint disorder. The literature on similar cases is reviewed, and the possible role of crystals and other aetiological factors is discussed. It is suggested that a characteristic form of large-joint atrophy can occur in elderly patients at a number of joint sites and in several different clinical settings.