Osteoprotegerin (OPG) and LGR4 are inhibitors of RANK signaling.30,50 Increases in RANKL have been found in the bone marrow of women with osteoporosis.49 Imbalance in this pathway may contribute to arthritis, osteolysis, and prosthesis loosening.51 Here, TNFRSF11B is linked to arthritic joint disease.