Recently, receptor activator of nuclear factor-kappaB ligand (RANKL), its receptor RANK, and the decoy receptor osteoprotegerin (OPG), have been identified as paracrine mediator of bone functions. The balance of RANKL/RANK and OPG is critical for osteoclastogenesis modulation and physiological bone remodeling. Osteopontin (OPN) is an extracellular glycosylate bone phosphoprotein and acts both as chemokine and cytokine. It is produced by osteoclast, macrophages, T cells, hematopoietic cells and vascular smooth muscle cells. It is present particularly at high concentration in the lamina limitans and cement line, suggesting its role in the initiation and termination of the bone turnover. Chronic arthritis are a group of rheumatic pathologies characterized by periodical continuous or desultory use of corticosteroids. The main aims of this study are to evaluate OPG, RANKL and OPN serum concentrations in patients affected by chronic arthritis and to compare the above results with those ones obtained by young healthy population. OPG, RANKL and OPN serum concentration has been measured by ELISA method both in 40 patients affected by chronic arthritis then in young healthy population of 81 subjects. The differences between the two considered groups have been analyzed using unpaired T-Student. The difference between the two groups is significant for considered variables: OPG: t = -6.54, p < 0.001; RANKL: t = -2.71, p = 0.008; OPN: t = 2.55, p = 0.01. These results suggest that RANKL/RANK system,OPG and OPN have important role in patients with chronic arthritis.