The molecular and cellular mechanisms driving the pathogenesis of osteoporosis in SCI are not well characterized, but Wnt signaling and receptor activator of nuclear factor-κB (RANK)/receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) signaling have been implicated [12,13,14]. This evidence concerns the gene TNFSF11 and osteoporosis.