SOX9 and osteoarthritis: To determine the molecular mechanism by which β‐catenin regulates downstream target genes, we examined CCL2 expression in Sox9‐deleted intervertebral disc tissue since CCL2 serves as a ligand for the chemokine receptor CCR2, which plays a critical role in leukocyte migration during inflammation [39, 40] and has been shown to play important roles in osteoarthritis (OA) development and OA pain [41].