Relationship Between Body Mass Index and Osteoarthritis for Single and Multisite Osteoarthritis of the Hand, Hip, or Knee: Findings From a Canadian Longitudinal Study on Aging

To determine whether an apparent association between hand osteoarthritis (OA) and adiposity is explained by the presence of OA at other joint sites.Data from the Canadian Longitudinal Study on Aging, first cycle, comprehensive cohort, were used. Respondents age 45-85 years (n = 18,279) were asked separate questions about doctor-diagnosed OA in the hand, hip, or knee. Multinomial logistic regression was used to investigate the relationship between all combinations of hand, hip, and knee OA and body mass index (BMI) and waist-to-height ratio (WHtR).OA was reported by 34.6% of respondents, 28.0% with OA at >1 joint site. Hand OA was not significantly associated with BMI after accounting for OA at other joint sites, with similar findings for WHtR. All joint site combinations containing the knee were strongly associated with BMI, with odds ratios (ORs) ranging from OR 2.92 (95% confidence interval [95% CI] 2.53-3.37) for knee OA only with obesity class I to OR 9.98 (95% CI 7.12-13.88) for multi-joint knee, hip, hand OA with obesity class II/III. BMI distributions including knee OA were broader and shifted to higher BMI levels than those for hand or hip OA.Apparent associations between hand OA and BMI may be explained by concurrent OA at other joint sites. Recognizing that OA is a multi-joint disease is crucial for studies of the associations of adiposity with OA in a particular joint, especially the hand. The association between knee OA and BMI appears to be distinct from those for OA at other joint sites.