The TLR9 signaling pathway and the autophagic response in periodontitis with arthritis have been reported to be sensitive to cathepsin K. The production of the autophagy proteins TFEB and LC3A/B, the secretion of the inflammatory mediators TNF-α and IL-6, the amount of macrophages, and TLR9 are all elevated in periodontitis with arthritis, aggravating bone destruction (96). Here, CTSK is linked to arthritic joint disease.