MicroRNAs (miRs) are - 22 nucleotide non-cording forms of RNA and exhibit tissue or developmental stage specific expression patterns. Recent findings show taht the expression of miR-140, which is specifically expressed in chondrocytes, is reduced in OA chondrocytes. Furthermore, knockdown of miR-140 in mice chondrocytes promotes arthritis in mice. In addition to this, several other miRs have also been shown to play important roles in chondrocytes. Thus, miRs should be critical factors for cartilage development and homeostasis.