Associations between the radiographic phenotypes and the presence of metabolic syndrome in patients with knee osteoarthritis.

Background: We aimed to investigate the associations between the radiographic phenotypes and the presence of metabolic syndrome (MetS) in patients with knee osteoarthritis (OA).

Methods: We evaluated women age 40 and over who presented to our outpatient clinics with knee pain and fulfilled the clinical and radiographic criteria for the classification of idiopathic OA of the knee. Patients were categorized into two groups concerning dominant radiographic phenotype. We included consecutive 50 patients in each group. All patients were evaluated in terms of MetS according to the revised diagnostic criteria of the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III), as well as the World Health Organization (WHO).

Results: Overall, MetS prevalence was found to be 79% according to the NCEP ATP III-MetS criteria and 65% according to the WHOMetS criteria. Prevalence of MetS was higher in the joint space narrowing (JSN)-dominant group compared to the osteophyte (O)- dominant knee OA group, but the difference did not reach statistical significance. However, in subgroup analysis (54 patients) in which we excluded patients with a past medical history of type 2 diabetes mellitus (DM), the prevalence of NCEP ATP III-MetS was statistically significantly higher in the JSN-dominant group compared to the O-dominant group [22 (75.9%) vs. 12 (48%), respectively, p = 0.03]. Logistic regression analysis in the subgroup demonstrated that the presence of NCEP ATP III-MetS was an independent risk factor for JSN-dominant knee OA phenotype [OR and 95% CI = 3.48 (1.09-11.13)].

Discussion: The prevalence of MetS is quite high in patients with knee OA and is particularly pronounced in patients with JSNdominant radiographic phenotype. Moreover, our results suggest that MetS is an independent risk factor for JSN-dominant knee OA in patients with no past medical history of DM.