INTRODUCTION: Osteoarthritis (OA) is a widely prevalent joint disease leading to motor disability and pain. Appropriate indicators for identifying patients at risk for this progressive disease, identifying molecular events for detecting early phases of the disease, or biomarkers to screen for treatment responses, however, are lacking. Micro RNAs (miRNAs), which play crucial roles in OA, could be potential biomarkers of OA. Because circulating miRNA levels reflect the disease state, they may be useful for OA screening and as diagnostic tools, reducing the need for invasive procedures and minimizing the cost of current diagnostic methods. MATERIALS AND METHODS: The expression levels of 18 microRNAs (let-7e-5p, miR-21-5p, miR-93-5p, miR-101-3p, miR-103a-3p, miR-130a-3p miR-146a-5p, miR-16-5p, miR-193b-3p miR-199a-3p, miR-210-3p, miR-222-3p, miR-22-3p, miR-27a-3p, miR-27b-3p, miR-335-5p, miR-454-3p, and miR-98-5p) were analyzed by quantitative real-time polymerase chain reaction in the cartilage tissues and serum samples of 28 OA patients and were compared to those of 2 healthy controls. RESULTS: Expression of microRNA-146a-5p was significantly upregulated in the cartilage (p=0.006) and serum (p=0.002) of OA patients. The expression levels of miR-146a-5p in the serum were positively correlated with those in the cartilage (Pearson correlation coefficient R=0.32; p=0.002). CONCLUSION: miR-146a-5p was significantly overexpressed in patients with OA, both in the articular cartilage tissue and serum, with a positive correlation between the levels in both types of samples. Therefore, the miR-146a-5p serum level could reflect the molecular processes in the cartilage, suggesting its clinical utility as a biomarker for OA management. Implementing noninvasive biomarker using serum miRNAs involves the analysis of the misregulated miRNAs linked to the cartilage pathology.