The objective of this study was to investigate serum MMP–7 levels in patients with knee osteoarthritis (OA) according to the radiographic disease severity.A cross–sectional study was done on 60 consecutive knee OA patients and 60 age and sex–matched healthy control participants.Disease severity in the knee OA population was assessed using the Kellgren–Lawrence (K–L) grading scale.Circulating MMP–7 levels were examined in serum using the Quantikine Human MMP–7–ELISA. Serum MMP–7 levels were significantly higher in knee OA patients than control groups. Significantly higher MMP–7 levels in severe degree were compared with mild degree of knee OA patients.Our results indi­cated that MMP–7 may play impor­tant roles in the pathogenesis of OA and also MMP–7 can be a potential biomarker to predict the severity of knee OA.