Although osteoarthritis (OA) has been suggested as another component of metabolic syndrome (MetS), weight-independent associations between MetS and knee OA or intensity of arthritic knee pain remain unclear.
The objective of the study was to evaluate the above associations and suggest possible mechanisms.
This was a cross-sectional study using the fifth Korean National Health and Nutrition Examination Survey (2010).
A total of 2363 adults (≥50 y of age) who had completed both laboratory examinations and an evaluation for radiographic knee OA participated in the study.
Radiographic knee OA was defined as a Kellgren/Lawrence grade of 2 or greater, and the intensity of arthritic knee pain was assessed using a self-reported numeric rating scale. MetS was diagnosed based on National Cholesterol Education Program-Adult Treatment Panel III criteria, and insulin resistance was evaluated using the homeostasis model assessment-estimated insulin resistance index.
In a multivariable logistic regression analysis, MetS was associated with radiographic knee OA (adjusted odds ratio 1.49; 95% confidence interval 1.23-1.79; P < .001). This association was not changed significantly after further adjusting for homeostasis model assessment-estimated insulin resistance but became nonsignificant after adjusting for weight or body mass index. Age-, sex-, and weight (or body mass index)-adjusted mean score of knee pain was significantly higher in subjects with more components of MetS (P for trend = .010 or .035, respectively).
The association between MetS and radiographic knee OA can be largely explained by an excessive weight but not by insulin resistance, a key pathophysiology of MetS. Because accumulation of MetS components appears to be associated with a higher intensity of knee pain, independently of weight, appropriate treatment for MetS may be helpful for subjects with knee pain.