BACKGROUND: The purpose of this study was to investigate the prevalence of metabolic syndrome and its co-morbidities in patients with primary knee osteoarthritis and to assess if the severity of metabolic syndrome, and components, correlates with the severity of osteoarthritis symptoms. METHODS: A case controlled analysis of 70 patients with osteoarthritis compared to a control group of 81 patients. Each patient underwent clinical review including history, examination, and pathology tests. The case-group all had stage IV osteoarthritis as determined by radiographs and intra-operative assessment. In addition a visual analogue scale (VAS), Hospital for Special Surgery knee score (HSS), and Hamilton Depression scores were completed. RESULTS: The prevalence of hypertension, obesity, dyslipidemia and metabolic syndrome was significantly higher in the patients with osteoarthritis compared to the control group. There is a significant correlation between the degree of hypertension, the presence of dyslipidemia or hyperglycemia and the severity of osteoarthritis symptoms. Variables hypertension, low HDL-C levels, and the number of co-morbidities were all identified as risk factors for increased osteoarthritis symptoms. CONCLUSIONS: There is a correlation between the number of metabolic disorders, the severity of hypertension and severity of osteoarthritis symptoms. Hypertension and decreased HDL-cholesterol were positive risk factors for increased osteoarthritis symptomatology.