The different influence of high levels of physical activity on the incidence of knee OA in overweight and obese men and women-a gender specific analysis

Abstract

Objective: To investigate the influence of physical activity on incidence of knee osteoarthritis (OA) in overweight and obese men and women.

Design: Data were extracted from the Osteoarthritis Initiative cohort on 1,667 participants without symptomatic knee OA at baseline. We used logistic regression and marginal effect models to estimate the effect of body mass index (BMI) and reported physical activity score, together with the interaction between them, on the development of radiographic knee OA, symptomatic knee OA and joint space narrowing (JSN) after 96-months.

Results: Men in the most active quartile had almost double the likelihood of knee OA, independent of OA definition [e.g., odds ratio (OR) 2.4 (95%CI: 1.2-4.5) for radiographic knee OA]. Interaction analyses showed statistically significant interactions between physical activity and BMI on developing knee OA (i) radiographic OA _interaction(P = 0.039), (ii) symptomatic OA _interaction(P = 0.022), (iii) JSN _interactionP = 0.012). The margin plots in men also demonstrated that the effect of physical activity on different measures of knee OA were modified by high levels of BMI. These effects were not mirrored in women where at all BMI levels, the level of reported physical activity did not influence likelihood of knee OA independent of OA definition.

Conclusions: In overweight and obese men, there appears to be a threshold above which increasing levels of physical activity are associated with higher risk of knee OA. This is absent in women.

Keywords: Knee; Obesity; Osteoarthritis; Physical activity.