Osteoprotegerin (OPG) and receptor activator of nuclear factor-κB (RANKL) protein expression at subchondral bone. Densitometric analysis of OPG, RAKL and OPG/RANKL ratio, as well as, representative Western Blot images for OPG and RANKL are shown. To perform this blot, 40 μg of total protein from subchondral bone was used for HEALTHY, OA, OP and OPOA groups (n = 6, each group). OA: osteoarthritis; OP: osteoporosis. Data are displayed as arbitrary units ± SEM. *P < 0.05 vs. HEALTHY, #P < 0.05 vs. OA, &P < 0.05 vs. OP.