The association of radiographic foot osteoarthritis and radiographic osteoarthritis at other sites

SummaryObjectiveTo quantify the association between radiographic foot osteoarthritis (OA) and radiographic OA at four joints: second distal interphalangeal (DIP), third proximal interphalangeal (PIP), first carpometacarpal (CMC), and the knee.MethodsData collected for the Clearwater Osteoarthritis Study (COS) were analyzed (N=3436). The study outcome was first metatarso-phalangeal joint (first MTP) OA status. The predictor variables were second DIP, third PIP, first CMC, and knee OA. The Kellgren and Lawrence scale determined OA status. The strength of the association between foot OA and other sites was further explored by unilateral and bilateral categories.ResultsFor both genders, we found a significant, positive relationship between grade 2+ foot OA and second DIP, third PIP, first CMC, and knee OA. This relationship maintained its significance after adjustment for age, body mass index, and occupational history. Adjusted odds ratios ranged from 3.2 for the second DIP joint (P<0.0001) to 3.7 for the knee joint (P