In both models, RANKL was shown to be the main driver of BMD loss not only in the hook but also in the vertebrae, whereas the proinflammatory cytokines TNF-α and IL-1, which are among the prominent factors crucial for the pathogenesis of RA, seem not to contribute to the vertebral osteoporotic phenotype [21,24,33]. Here, TNF is linked to rheumatoid arthritis.