The role of lifestyle factors on knee structure in a community-based population: a longitudinal study

Knee osteoarthritis (OA) is a major cause of pain and disability and accounts for approximately 90% of knee replacements. The prevalence of knee OA is expected to increase given the ageing and obesity epidemic of the population. To date, most research has focused on treating the resulting pain and disability. However, in order to reduce the burden of OA, identifying modifiable risk factors in the normal population is important. This study aims to identify lifestyle factors (diet, physical activity and body composition) that affect knee cartilage and bone in asymptomatic subjects without clinical knee OA, thereby identifying potential targets for the prevention of knee OA. This will be done by utilizing an existing cohort, the Melbourne Collaborative Cohort Study (MCCS), with over 15 years of prospectively collected risk factor data, and recently developed methodology for measuring articular cartilage volume that our group has pioneered. This study was a longitudinal cohort study over 2 years. 297 asymptomatic participants, with no significant trauma or known arthritis, were recruited from the MCCS. There was 15 year of prospectively collected data already available as part of the MCCS regarding detailed dietary intake, weight, body mass index, body composition, and physical activity. Each participant underwent a knee magnetic resonance imaging (MRI) during 2003-2004 and 2 years later. Physical dysfunction (the Western Ontario and McMaster Universities Osteoarthritis Index), physical activity, body composition, and past and current occupational history were collected at the time of MRI. Changes in knee cartilage volume, cartilage defects and bone marrow lesions over 2 years were assessed from MRI using validated methods. Analyses of the change in cartilage volume, cartilage defects and bone marrow lesions associated with lifestyle factors will be performed using linear/logistic regression, adjusting for confounders.