MMP13 and osteoarthritis: Though subchondral bone clearly contributes to osteoarthritis, the role of osteocytes in joint disease remains unclear.3,5–8 Given the strong association of PLR suppression with cartilage degeneration in human OA (Figs. 1–3), we tested the hypothesis that PLR suppression via ablation of osteocyte MMP13 is sufficient to cause cartilage degeneration.