Nitric oxide levels and superoxide dismutase enzyme activity in synovial fluid of patients with knee osteoarthritis

Objectives: We investigated nitric oxide (NO) levels and superoxide dismutase (SOD) enzyme activity in synovial fluid of patients with primary knee osteoarthritis (OA). Patients and methods: The study included 36 patients (31 females, 5 males; mean age 63 years; range 48 to 88 years) with knee OA according to the diagnosis criteria of American College of Rheumatology. Radiographic severity of OA was assessed according to the Kellgren-Lawrence grading system. Synovial fluid samples were taken by needle aspiration before knee arthroplasty or hyaluronic acid injection and stored at -80 degrees C in Eppendorf tubes. Nitrite and nitrate levels were determined by the spectrophotometric method based on the Griess reaction. Total SOD activity was determined by the spectrophotometric method. The results were compared with those of 10 controls (6 females, 4 males; mean age 49 years; range 26 to 70 years) who clinically and radiographically had normal knees, but underwent arthroscopic examination for knee pain of unknown origin. Results: Compared to controls, NO levels were significantly higher and SOD activity was significantly lower in patients with OA (p < 0.001). No significant differences were found between radiographically graded groups with regard to NO level and SOD activity (p > 0.05). Conclusion: Our data suggest that NO acts as a potent mediator of cartilage damage and SOD as an antioxidant mediator in OA. Further studies are needed to clarify the clinical significance of these parameters.