Objective It was aimed to determine the relationship between osteoprotegerin (OPG) levels and disease activity and severity in patients diagnosed with knee osteoarthritis (gonarthrosis).

Materials and Methods: Sixty patients diagnosed with gonarthrosis according to the classification criteria of the American College of Rheumatology (ACR) and 30 healthy control subjects were included in the study. Radiographic grading of gonarthrosis was done according to the Kellgren-Lawrence (KL) classification. According to the KL classification, the patients were divided into 3 stages as KL2, KL3 and KL4. Visual analog scale (VAS) and Western Ontario and MacMaster osteoarthritis index (WOMAC) were used to assess function and pain. Serum OPG levels were measured by Enzyme-Linked Immunosorbent Assay (ELISA) method.

Results: There was no statistical difference between the patients with gonarthrosis and the control group in terms of age and gender (p=0.856, p=0.941, respectively). Mean serum OPG levels were found to be 269.90±173.54 pg/mL in the group with gonarthrosis and 114.07±58.53 pg/mL in the control group. Mean serum OPG levels were statistically significantly higher in the gonarthrosis group compared to the control group (p<0.001). OPG levels were statistically higher in KL4 stage than in KL3 and KL2 stages (434.25±221.55 pg/mL, 252.73±100.56 pg/mL, 188.81±71.77 pg/mL, p=0.044, p<0.001, respectively). A positive correlation was found between serum osteoprotegerin, WOMAC index and VAS in patients with gonarthrosis (r=0.25, p=0.042, r=0.27, p=0.032, respectively).

Conclusions: Our study revealed that OPG may be a biological marker reflecting the radiological findings of joint destruction in gonarthrosis.