Early detection of osteoporosis can be made at any age by measuring bone mineral density (BMD), in order to identify those individuals who need intervention for preventing fractures. According to the recommendations of a WHO task force, osteoporosis is defined in women as a BMD that lies 2.5 standard deviations or more below the average for the young healthy female population. The same absolute BMD value can be utilized for men. The preferred site for diagnostic assessment, particularlyin the elderly, is the hip, using dual X-ray absorptiometry. Many studies indicate that the risk of fragility fractures increases progressively as BMD declines, and that there is a close relationship between the prevalence of osteoporosis, as assessed accordingly to the WHO criteria, and the incidence of fractures.