Objectives: To determine in a large prospective population-based cohort study relationships between different measures of body mass and incidence of severe knee and hip osteoarthritis (OA) defined as arthroplasty of knee or hip due to OA.
Materials and methods: Body mass index (BMI), waist circumference, waist-hip ratio (WHR), weight, and percentage of body fat (BF%) was measured at baseline in 11026 men and 16934 women, 45 to 73 years old, from the general population. Incidence of severe OA was defined as arthroplasty due to knee or hip OA monitored over 11 years of follow-up by linkage with the Swedish hospital discharge register.
Results: During follow-up, 471 individuals had knee OA and 551 had hip OA. After adjustment for age, sex, smoking and physical activity, the relative risks (RR) of knee OA (4th vs. 1st quartile) were 8.1 (95% CI 5.3-12.4) for BMI, 6.7 (4.5-9.9) for waist circumference, 6.5 (4.6-9.43) for weight, 3.6 (2.6-5.0) for BF% and 2.2 (1.7-3.0) for WHR. The corresponding RR for hip OA were 2.6 (2.0-3.4) for BMI, 3.0 (2.3-4.0) for weight, 2.5 (1.9-3.3) for waist, 1.3 (0.99-1.6) for WHR and 1.5 (1.2-2.0) for BF%.
Conclusions: All measures of overweight were significantly associated with incidence of knee OA leading to arthroplasty, with the strongest relative risk gradient observed for BMI. Even though incidence of hip OA showed smaller differences between normal weight and obesity, body mass was a significant risk factor also for hip OA leading to arthroplasty. Our results support a major link between overweight and biomechanics in increasing knee and hip OA risk in both men and women, but do not exclude a contributing role of metabolic factors associated with adipose tissue.