The influence of patterns of usage on the structure and function of the hands was formally tested. Three groups of female textile workers, each employed in a distinct and defined, atraumatic, repetitive, stereotyped manual task for at least 20 years, were identified in a single rural mill. Replicate data were obtained for the following measures of structure and function: range of motion, a score for the degree of radiographic degenerative changes at each hand joint, malalignment at digital joints determined radiographically, and a quantitative measure of osteophyte formation. Significant and consistent differences in the right hand when compared to the left were detected. Furthermore, highly significant task-related differences were demonstrated. These task-related differences in the structure and function of the hands were consistent with the pattern of usage. Therefore these three patterns of usage influence hand structure and function in the population studied.Primary degenerative joint disease (DJD) of the hand as a clinical entity is clearly multifactorial in pathogenesis. Literature spanning several decades documents the heritability of the condition (1,2) and the distinctive clinical patterns of involvement (3,4). Such data have appropriately focused research efforts on understanding the pathobiology of the diarthrodial joint and, more particularly, the underlying biochemical derangements in hyaline cartilage (5,6). The role of use in pathogenesis is less clear. It has been argued that the microtrauma of use might have a primary role in the pathogenesis of DJD (7) including DJD of the hand (8,9).The hypothesis of a more primary pathogenetic role for usage leads to a corollary hypothesis: The pattern of usage should influence structure and function of the hand in a fashion compatible with the clinical definition of DJD. Furthermore, such a corollary hypothesis lends itself to formal testing, that is, the formulation and testing of the null hypothesis that there is no clinically detectable difference in the structure and function of the hands of groups of subjects, each with distinct and dif-