Introduction: As the prevalence of osteoarthritis (OA) increases with age, the coexistence of other chronic diseases is common. Objectives: To evaluate the frequency of comorbidities in OA patients and to measure their impact on pain and physical function of those patients. Methods: Cross-sectional study in OA patients of a public rheumatology clinic. Pain was measured by use of the Visual Analogue Scale (VAS) and physical function by use of the Lequesne's and SACRAH indices. A screening for depression was performed, as were the following measurements: anthropometric data; blood pressure; fasting glycemia; and lipid profile. Results: The study assessed 91 patients (mean age 59.3 years; 91.4% female). The metabolic syndrome frequency was 54.9%. Hypertension occurred in 75.8% of the patients, dyslipidemia in 52.6%, and obesity in 57.1%. The screening for depression was positive in 61.3% of patients. When comparing the metabolic syndrome components individually, patients with hypertension had higher SACRAH scores, with statistically significant differences (P = 0.035). For the other variables, no differences among the Lequesne's, SACRAH and VAS scores were observed. Conclusion: This group of OA patients showed a high frequency of depression, metabolic syndrome and its components in isolation, which can impact the pain and physical function of those patients. Such results showed the need for investigating and treating those comorbidities in OA patients.