Osteoarthritis, which is commonly thought of as a degenerative joint disease related to mechanical factors and/or age-related changes in articular cartilage, has recently been shown to be associated with the metabolic syndrome.
For example, patients who develop osteoarthritis at the mean age of the general population have a ~5-fold increased risk of metabolic syndrome even when controlling for obesity. An association has also been found between popliteal artery wall thickness and generalized osteoarthritis, even after controlling for sex, age, and body mass index. In addition, knee osteoarthritis is more common in obese women with metabolic syndrome than in obese women without metabolic syndrome.
Several mechanisms have been put forward for this association: Impaired expression of genes regulating cholesterol metabolism in cartilage, impaired blood flow to bone from endothelial cell damage caused by hypertension, high glucose concentrations leading to reactive oxygen species in chondrocytes, and abnormalities in leptin production by osteoblasts leading to cartilage destruction.
These findings suggest that a common set of factors underlies the development of both osteoarthritis and the metabolic syndrome, and that the development of osteoarthritis isn't simply due to the repetitive microtrauma from obesity. Some have even suggested that the finding of osteoarthritis should prompt a cardiovascular workup.
- Katz JD, Agrawal S, Velasquez M. Getting to the heart of the matter: osteoarthritis takes its place as part of the metabolic syndrome. Curr Opin Rheumatol. 2010 Sep;22(5):512-9.
- Kornaat PR, Sharma R, van der Geest RJ, Lamb HJ, Kloppenburg M, Hellio le Graverand MP, Bloem JL, Watt I. Positive association between increased popliteal artery vessel wall thickness and generalized osteoarthritis: is OA also part of the metabolic syndrome? Skeletal Radiol. 2009 Dec;38(12):1147-51.