Synovial Fluid Omentin-1 Levels Are Inversely Correlated With Radiographic Severity of Knee Osteoarthritis

Objective: The purpose of this study was to demonstrate omentin-1 levels in serum and synovial fluid (SF) of patients with knee osteoarthritis (OA) and to investigate their correlation with radiographic disease severity. Methods: One hundred and ninety-seven patients with OA and 65 sex-and age-matched healthy controls were enrolled in this study. The radiographic disease severity of OA was assessed by the Kellgren- Lawrence (KL) grading system. The omentin-1 levels in serum and SF were determined by enzyme-linked immunosorbent assay. Results: There were no significant differences in serum omentin-1 levels between patients with OA and healthy controls (P > 0.05). There were also no significant differences in serum omentin-1 levels among patients with OA with different KL grades (P > 0.05). However, SF omentin-1 levels decreased significantly as the KL grades increased (KL grade 4 < KL grade 3 < KL grade 2; all P < 0.01) in the patients with OA. Furthermore, SF omentin-1 levels were negatively correlated with KL grades (r = -0.643; P < 0.001). Multinomial logistic regression analysis revealed that there was still a negative correlation between the SF omentin-1 levels and the KL grades after adjusting for confounding factors (P < 0.001). Conclusions: Synovial fluid omentin-1 levels showed an independent and negative correlation with radiographic severity of the disease in patients with knee OA. Omentin-1 in SF might serve as a potential biomarker for reflecting the degenerative process of primary knee OA.