The relation between body mass index and waist-hip ratio in knee osteoarthritis.

Background: The best measure of body habitus as a risk factor for chronic disease is not well defined. Our intent was to examine the relation between waist-hip ratio (WHR) and body mass index (BMI) as a measurement of body habitus in patients with end-stage knee osteoarthritis (OA).

Methods: We reviewed the data of 200 consecutive patients in our registry undergoing knee replacement surgery for demographic data of age, sex, BMI and WHR. We performed a stratified analysis by sex and calculated the risk ratios (RRs) to describe the risk of being classified as obese by WHR for those considered obese by the BMI criteria.

Results: A similar percentage of male and female patients were classified as obese by the BMI criteria (38% v. 42%, respectively). Men were classified as obese more often than women by WHR (92% v. 82%). The RR of being obese as determined by WHR if classified as obese by the BMI criteria was 1.04 (95% confidence interval [CI]0.91-1.18) for men and 1.23 (95% CI 1.03-1.46) for women.

Conclusion: Among patients with knee OA, the overlap between BMI and WHR is greater in women than men. This difference has implications for defining the prevalence of metabolic syndrome in this population.