Recent advances in both the pharmacological and surgical treatment of osteoporosis and vertebral compression fractures offer exciting new options for elderly patients. However, these treatments should be considered only with an indepth knowledge of osteoporosis as a metabolic disorder with complex effects on bone, its homeostatic regulation, and vertebral strength. Bone homeostasis is under the influence of both endogenous hormonal changes and external mechanical loads resulting from physical activity. These impart their effects through regulation of the relative activities of bone cells, in particular osteoblasts and osteoclasts, which control bone deposition and resorption, respectively. The strength of a vertebra is directly influenced by the amount and relative proportions of its components, with bone mineral density a useful measure of fracture risk. The purpose of this article is to discuss these issues, among others, in order to offer the reader a better understanding of the pathophysiology of osteoporosis and the determinants of bone strength as they relate to the aging skeleton.