OPG, on the other hand, had a significant positive correlation with age in the osteoporosis group (r = 0.29, p < 0.05), while it was inversely correlated with femoral neck left BMD (r = −0.56, p < 0.001) and femoral neck right BMD (r = −0.37, p < 0.05) in the same group. This evidence concerns the gene TNFRSF11B and osteoporosis.