Immunohistochemistry. (A) Expression of matrix metalloproteinase 13 (MMP-13), ADAMTS5 and cathepsin K in representative sections of cartilage (MMP-13 and ADAMTS5) and subchondral bone (cathepsin K) from placebo-treated dogs with osteoarthritis (OA) and tiludronic acid (TA: 2 mg/kg/2 weeks)-treated dogs with OA. Positive cells are shown by dark brown staining (original magnification ×100). (B) Levels of MMP-13, ADAMTS5 and cathepsin K as determined by immunostaining. The values are expressed as the mean ± SEM. P-values were calculated by using a generalized linear model under logistic polytomous distribution function using the proportional odds assumption.