Calcitonin gene-related peptide can be selected as a predictive biomarker on progression and prognosis of knee osteoarthritis

Purpose The purpose of this study was to examine calcitonin gene-related peptide (CGRP) concentrations in serum and synovial fluid of patients with primary knee osteoarthritis (OA) and healthy controls and to explore their relationship with clinical and radiographic severity of OA. Methods Sixty-five patients with primary knee OA and 21 healthy controls were recruited. CGRP concentrations in the serum and synovial fluid were measured using enzyme-linked immunosorbent assays. The radiographic severity of OA was evaluated using the Kellgren and Lawrence (KL) classification. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC) was used to assess pain, stiffness and physical function. Results Serum and synovial fluid CGRP concentrations tended to be higher with the increase in KL grades (r = 0.565 and r = 0.441, P < 0.001, respectively), and were significantly positively correlated with KL grades, total WOMAC score and each subscale (pain, stiffness and physical function). Conclusions The result demonstrated that CGRP in serum and synovial fluid was related to progressive joint damage in knee OA. CGRP can be selected as a biomarker for monitoring disease severity and could be a predictive role on prognosis and progression of knee OA.