Cathepsin family of proteases contains several diverse classes of enzymes. The cysteine protease class comprises cathepsin B, H, K, L, O, and S. The aspartyl protease class contains cathepsin D and E. Cathepsin G belongs to the serine protease class. Cathepsins are involved in various cellular events such as peptide biosynthesis, protein degradation, and apoptosis. Cathepsin K expression is highest in bone, cartilage, and skeletal muscle