The role of inflammatory cytokine network in inflammatory bone loss. Bone remodeling is tightly regulated by the balanced action between bone-forming osteoblasts and bone-resorbing osteoclasts. In chronic inflammatory condition, inflammatory cytokine networks induce an uncoupling of bone formation and resorption that result in significant inflammatory bone loss. RANK: receptor activator of nuclear factor κB. RANKL: RANK ligand. OPG: osteoprotegerin. Runx2: runt-related transcription factor 2. TRAP: tartrate-resistant acid phosphatase. NFATc1: nuclear factor of activated T cells cytoplasmic 1. v-ATPase: vacuolar-type H+-ATPase. MMP: matrix metalloproteinase. Ctsk: cathepsin K.