Relationship of height, weight and body mass index to the risk of hip and knee replacements in middle-aged women

Objectives: To examine the effect of height, weight and body mass index (BMI) on the risk of hip and knee replacement in middle-aged women. Methods: In a prospective cohort study 490 532 women aged 50-69 yrs who were recruited in the UK in 1996-2001 were followed over 2.9 yrs for incident primary hip and knee replacements. Results: Height, weight and BMI were all associated with the risk of hip and knee replacement. Comparing the tallest group (≥170 cm) with the shortest (<155 cm) the relative risks were 1.90 (95%CI 1.55-2.32) for hip replacement and 1.55 (95%CI 1.19-2.00) for knee replacement. Comparing the heaviest group (≥75 kg) with the lightest (<60 kg) the relative risks of hip and knee replacement were 2.37 (95%CI 2.04-2.75) and 9.71 (95%CI 7.39-12.77), respectively. Comparing obese women (BMI<30 kg/m2) to women with a BMI