Acidic cysteine endoproteinase cathepsin K in the degeneration of the superficial articular hyaline cartilage in osteoarthritis

Acid-activated, but pharmacologically inhibitable, cathepsin K is induced in phenotypically altered chondrocytes in OA. The findings suggest that cathepsin K, rather than neutral matrix metalloproteinases, degrades the superficial gliding surfaces of the articular hyaline cartilage in OA.