SOX9 and osteoarthritis: On the other hand, a recent report showed that the postnatal ablation of Sox9 dramatically decreases type II collagen mRNA and aggrecan contents; however, no histopathological signs of osteoarthritis were observed [52], indicating that the amount of extracellular matrix in articular cartilage is important but may not be necessary for the development of degradative changes in articular cartilage.