The enzyme's ability to catabolize elastin, collagen, and gelatin allows it to break down bone and cartilage.

This catabolic activity is also partially responsible for the loss of lung elasticity and recoil in emphysema.

Cathepsin K is expressed in a significant fraction of human breast cancers, where it could contribute to tumor invasiveness.

[7] Mutations in this gene are the cause of pycnodysostosis, an autosomal recessive disease characterized by osteosclerosis and short stature.

[16][17][18] Medivir has a cathepsin K inhibitor, MIV-711 (L-006235[19][20][21]), in Phase IIa clinical trial, as a disease modifying osteoarthritis drug, as of October 2017.