TGFB1 and osteoarthritis: Moreover, elevated levels of TGF‐β, insulin growth factor‐I (IGF‐I), and IGF‐II have been observed in cultures of human osteoarthritic subchondral bone osteoblasts and in cortical bone explants from the iliac crest of patients affected by osteoarthritis, suggesting an increased biosynthetic activity of osteoblasts (Dequeker et al., 1993; Massicotte et al., 2006).