Recent studies have confirmed that BMP-7 is a strong chemotactic component in cartilage cells produced by mesenchymal stem cells, and it can promote cartilage cells to secrete specific extracellular matrix (proteoglycans and collagen type II). And BMP-7 can induce the differentiation of BM-MSCs into cartilage cells, and that it offers a greater efficiency in repairing cartilage and subchondral bone defects (16) .