RESUMO
To investigate osteopontin [OPN] levels in both plasma and synovial fluid of patients with primary knee osteoarthritis [OA] and their relationship with radiological grade. Sixty patients had knee OA and 30 control subjects were included. Anteroposterior knee radiographs were taken to determine the disease severity of the affected knee. The radiographic grading of OA in the knee was performed by using the Kellgren-Lawrence grading. Osteopontin levels in the plasma and synovial fluid were measured using enzyme-linked immunosorbent assay and compared. OA patients had higher plasma osteopontin concentrations compared to healthy controls [p < 0.000]. Osteopontin levels in synovial fluid were significantly higher with respect to plasma sample [r = 0.694, p < 0.000]. The mean plasma levels of osteopontin in KL grade 4 were greater than those in KL grade 3, and the difference was statistically significant [p < 0.01]. The plasma osteopontin levels significantly correlated with the severity of disease [r = 0.870, p < 0.000]. The synovial fluid levels of osteopontin also correlated with disease severity as regarding the radiological grade [r = 0.817, p < 0.000]. Osteopontin in plasma and synovial fluid is related to progressive joint damage in knee OA. Osteopontin may serve as a biochemical marker for determining disease severity as regarding radiological grade