Objective: To examine the association between body mass index (BMI) and osteoarthritis (OA) leading to total hip (THR) or knee (TKR) joint replacement.
Methods: Case-control study design. All patients still living in Iceland that had had a THR or TKR due to OA until the end of 2002 were invited to participate. First degree relatives of participating patients served as controls. N=1,473 cases (872 women) and n=1,103 controls (599 women), all born between 1910 and 1939 and that had answered a questionnaire including information about height and weight were analyzed. A randomly selected sample, representative of the Icelandic population, was used as a secondary control group.
Results: The odds ratio (OR), adjusted for age, occupation, and the presence of hand OA, for overweight men getting a THR was 1.1 (95% confidence interval [95% CI] 0.9-1.5) and for obese men the OR was 1.7 (95% CI 1.0-2.9). The OR for overweight men getting a TKR was 1.7 (95% CI 1.1-2.6) and for obese men the OR was 5.3 (95% CI 2.8-10.1). For overweight women the OR for getting a THR was 1.0 (95% CI 0.8-1.3) and for obese women 1.0 (95% CI 0.6-1.5). For overweight women the OR for getting a TKR was 1.6 (95% CI 1.1-2.2) and for obese women the OR was 4.0 (2.6-6.1).
Conclusion: Our study supports a positive association between high BMI and TKR in both sexes, but for THR the association with BMI seems weaker, or for women possibly negligible.