Incidence of total knee and hip replacement for osteoarthritis in relation to the metabolic syndrome and its components: A prospective cohort study

Objective: To examine whether components of metabolic syndrome (MetS), either singly or additively, were associated with the incidence of severe knee and hip OA, and whether these associations were independent of obesity assessed by body mass index (BMI). Methods: Twenty thousand, four hundred and thirty participants who had blood lipids, anthropometric and blood pressure measurements during 2003-2007 were selected from the Melbourne Collaborative Cohort Study. MetS was defined as central obesity assessed by waist circumference and any two of raised triglyceride level, reduced HDL cholesterol level, hypertension or impaired fasting glycaemia. The incidence of total knee and hip replacement was determined by linking cohort records to the Australian Orthopaedic Association National Joint Replacement Registry. Results: Six hundred and sixty participants had knee OA and 562 had hip OA. After adjustment for age, gender, country of birth, education, physical activity and BMI, central obesity [hazard ratio (HR) 1.59, 95% confidence interval (Cl) 1.25-2.01] and hypertension (1.24,1.05-1.48) were associated with increased risk of knee OA. The accumulation of MetS components was associated with knee OA risk, independent of BMI: one component, 2.12(1.15-3.91); two components, 2.92(1.60-5.33) and three or more components, 3.09 (1.68-5.69). No statistically significant associations were observed for hip OA. Conclusion: Cumulative number of MetS components and central obesity and hypertension were associated with increased risk of severe knee OA, independent of BMI. No associations were observed with severe hip OA. These findings suggest that the pathogenesis of knee and hip OA differ and that targeting the management of MetS may reduce the risk of knee OA. (C) 2014 Elsevier Inc. All rights reserved.