33). PKC-mediated mitogen-activated protein kinase, activated by TGF-β-stimulated Wnt-5a overexpression, signals for chondrogenic differentiation into functional cells (Ref. 50). VEGF is hypothesized to mediate cartilage catabolism and endochondral ossification in OA (Ref. 51), and since VEGF upregulation is significant under hyperglycaemic conditions (Ref. 52), the higher VEGF expression in OA with DM compared with OA is coherent (Ref. 34). SOX9, a chondrocyte-protecting factor commonly downregulated in OA, is further reduced in OA with DM (Refs 25, 53). This evidence concerns the gene WNT5A and diabetes mellitus.