Genetic factors play a major role in the expression of OA; however, the influence of heredity varies in different joints.9 Susceptibility to OA has been investigated by genome-wide linkage of families with OA and candidate gene association studies in unrelated individuals.9 No specific genes for predicting OA have been identified yet, but those that regulate the synthesis of the various components of cartilage rather than coding for specific structural proteins offer the greatest promise. Current evidence suggests that the influence of heredity on OA development is greater in women than in men—as high as 60% for hand and hip OA, but considerably lower for knee OA (estimates range from 10% to 39%).9 In several epidemiologic studies, the influence of inheritance in knee OA was too low for linkage information to be determined.10