Background <p>The dysfunction of osteoblasts has been identified as a pivotal contributor to bone erosion in rheumatoid arthritis (RA). Emerging evidence shows long non-coding RNAs (lncRNAs) as important regulators in various pathological processes, including RA. However, the specific regulatory mechanisms of lncRNAs in osteoblast dysfunction of RA remain poorly understood and worth further investigation.</p> Methods <p>Collagen induced arthritis (CIA) rat model was established, tarsal tissue was isolated for sequencing of lncRNAs. The differentially expressed lncRNA was screened and verified in vivo and in vitro. The target microRNA of lncRNA and the target protein of microRNA were predicted by bioinformatics analysis and validated. The biology function of the lncRNA and microRNA was further investigated by knockdown or overexpression experiment in murine osteoblastic cell MC3T3-E1.</p> Results <p>LncRNA MIAT was highly expressed in tarsal tissue and serum of CIA rat as well as TNF-α-induced osteoblasts, and its high expression was negatively correlated with the expression of bone formation marker osteocalcin. Functionally, knockdown of lncRNA MIAT promoted the proliferation and mineralization of osteoblasts. Mechanistically, lncRNA MIAT directly bound to let-7i-5p and exerted a negative regulatory influence on its expression. CKIP-1 was a target of let-7i-5p. Overexpression of let-7i-5p promoted osteoblast proliferation and mineralization by targeting CKIP-1.</p> Conclusions <p>Taken together, this study demonstrated that lncRNA MIAT was involved in the regulation of osteoblast proliferation and mineralization through the lncRNA MIAT/let-7i-5p/CKIP-1 axis in RA.</p>