Introduction:Bone erosion is a central feature of rheumatoid arthritis (RA),which results from excessive osteoclast-mediated bone resorption and inadequate osteoblast-mediated bone formation.Evidences have demonstrated that the capacity of osteoblasts to repair articular bone erosions is impaired in RA.Casein kinase-2 interacting protein-1 (CKIP-1) is an intracellular negative regulator of osteogenic lineage activity.