AbstractA role of microRNAs (miRNAs), which are ∼22‐nucleotide non‐coding RNAs, has recently been recognized in human diseases. The objective of this study was to identify the expression pattern of miRNA (miR)‐210, known to be associated with angiogenesis, in bone from patients with osteonecrosis (ON) of the femoral head. The expression of miR‐210 in bone from 10 patients with osteoarthritis (OA) of the hip and ten with ON was analyzed by quantitative reverse transcription‐polymerase chain reaction (RT‐PCR) and by in situ hybridization. In addition, immunohistochemical staining for von Willebrand factor (vWF) and vascular endothelial growth factor (VEGF) was performed to identify the miR‐210 expressing cells. We found that in ON samples, the expression of mature, primary miR‐210, VEGF, matrix metalloproteinase (MMP)‐2, and MMP‐7 was significantly higher than that of OA samples. Section in situ hybridization of mature miR‐210 revealed that mature miR‐210 is expressed around the necrotic area. vWF and VEGF were also strongly expressed in the miR‐210 expressing cells. This study shows that miR‐210 is intensely expressed in ON, and might play a role in ON pathogenesis. The present study provides a solid basis for further functional analyses of miRNAs in ON. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1263–1270, 2012