Familial aggregation of osteoarthritis: data from the Baltimore Longitudinal Study on Aging.

To evaluate the familial aggregation of osteoarthritis (OA) in a cohort of healthy volunteers drawn from a community setting. Hand radiographs obtained between 1978 and 1991 and bilateral standing knee radiographs obtained between 1984 and 1991 were read for changes of OA, using Kellgren-Lawrence (K-L) scales. The hand sites were distal interphalangeal (DIP) joints, proximal interphalangeal (PIP) joints, and first carpometacarpal (CMC1) joints. For each joint group, the presence of OA in at least 1 joint in a joint group, the number of affected digits in each joint group, and the sum of the K-L grade across all joints were analyzed. Polyarticular OA was recorded if there were OA findings in 2 of 3 hand joint groups plus 1 or both knees. Data from 167 families with hand radiographs, 157 families with knee radiographs, and 148 families with both hand and knee radiographs were analyzed for sib-sib correlations. After adjustment for age, sex, and body mass index, clinically relevant sib-sib common correlations were found for OA of the DIP, PIP, and CMC1 joints, for OA at 2 or 3 hand sites, and for polyarticular OA (r = 0.33-0.81) when OA was defined according to the number of affected joints or as the sum of the K-L grade across all joints. These results from a cohort of volunteers drawn from a community setting and ascertained without regard to OA status demonstrate familial aggregation of OA and contribute to the evidence for heritability of OA.