Osteoprotegerin changes in saliva and serum of patients with knee osteoarthritis

The scope of this study was to assess salivary and serum osteoprotegerin (OPG) levels in knee osteoarthritis (OA). Serum and saliva OPG levels of 30 knee OA and 30 matched healthy controls in this cross-sectional study was assessed by ELISA. Knee pain was assessed by WOMAC. Data were analyzed by Student's t-test, Spearman correlation test and ROC. The mean serum but not saliva OPG level was lower in knee OA than that of the healthy group. WOMAC negatively correlated with serum OPG (r = -0.501; P = 0.000). The serum OPG cutoff value was 237.5 pg/ml for the diagnosis of knee OA. As serum OPG was lower in knee OA and negatively correlated with WOMAC, it seems that detection of OPG in serum but not in saliva may be a probable marker to the diagnosis of knee OA. Osteoprotegerin decreases in knee osteoarthritis.