Body weight changes and corresponding changes in pain and function in persons with symptomatic knee osteoarthritis: A cohort study

Objective To determine if a dose-response relationship exists between percentage changes in body weight in persons with symptomatic knee osteoarthritis (OA) and self-reported pain and function. Methods Data from persons in the Osteoarthritis Initiative (OAI) and the Multicenter Osteoarthritis (MOST) study data sets (n = 1,410) with symptomatic function-limiting knee OA were studied. For the OAI, we used baseline and 3-year followup data, while for the MOST study, baseline and 30-month data were used. Key outcome variables were Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function and pain change scores. In addition to covariates, the predictor variable of interest was the extent of weight change over the study period divided into 5 categories representing different percentages of body weight change. Results A significant dose-response relationship (P < 0.003) was found between the extent of percentage change in body weight and the extent of change in WOMAC physical function and WOMAC pain scores. For example, persons who gained =10% of body weight had WOMAC physical function score changes of -5.4 (95% confidence interval -8.7, -2.00) points, indicating worsening physical function relative to the reference group of persons with weight changes between <5% weight gain and <5% weight reduction. Conclusion Our data suggest a dose-response relationship exists between changes in body weight and corresponding changes in pain and function. The threshold for this response gradient appears to be body weight shifts of =10%. Weight changes of =10% have the potential to lead to important changes in pain and function for patient groups as well as individual patients.