To investigate the gene expression and potential functions of transforming growth factor-beta1 in osteophyte development.A total of 25 specimens were obtained from individuals undergoing total knee arthroplasty due to severe primary osteoarthritis. Tissue samples were embedded in paraffin wax and made into sections. Hematoxylin and eosin and toluidine blue stainings were performed. The expressions of collagen I, IIa, IIb, and X were detected by immunohistochemistry. Based on the histomorphology of cellularity and matrix abundance, the glycosaminoglycans content, and the differential expressions of collagen I, IIa, IIb, and X, the osteophytic tissues were classified. For each different type of osteophyte, expressions of transforming growth factor-beta1 were detected by immunohistochemistry and in situ hybridization, and results were analyzed using the image analysis system.Five different types of osteophytes were identified as type I, type II, type III, type IV, and type V. Transforming growth factor-beta1 mRNA was more and intensely expressed in chondrocytes of type II and III osteophytes, and was less in other types of osteophytes. The difference was significant (P<0.05, P<0.01).Transforming growth factor-beta1 mRNA is mainly expressed in early-mid stages of osteophytes and may play an important role in promoting the proliferation and differentiation of chondrocytes in the early stages of osteophyte development.