The effect of body composition and physical activity on hip structure in a community-based population without clinical hip osteoarthritis

Hip osteoarthritis (OA) is a major cause of pain and disability with no treatment that affects progression of disease. The prevalence of hip OA is expected to increase given the ageing of the population and the current obesity epidemic. To date, most research has focused on treating the resulting pain and disability. In order to reduce the burden of OA, identifying modifiable risk factors in the normal population, which have implications for the prevention of hip OA, is important. How obesity and physical activity affect the risk of hip OA has not been well understood. This study aims to examine the associations between body composition (muscle mass and fat mass) and physical activity over 15 years with hip structure assessed using magnetic resonance imaging (MRI), in order to identify strategies to protect the hip joint and prevent the onset of hip OA. This study was a cross-sectional study. 214 asymptomatic participants, with no significant trauma or known arthritis, were recruited from the Melbourne Collaborative Cohort Study. Weight, body mass index, body composition, and physical activity were measured in 1990-4, 1995-8 and 2003-5. Each participant underwent a hip MRI during 2009-2010. Weight, physical activity, and occupational history were obtained at the time of hip MRI. Hip cartilage volume, hip bone shape and the presence of bone marrow lesions were assessed from MRI using validated methods. Analyses of hip structure associated with body composition and physical activity will be performed using linear/logistic regression, adjusting for confounders.