More than 1.5 million osteoporosis-related fractures occur each year in the United States. Osteoporotic fractures most often involve the femoral neck, the vertebral bodies, or the wrist. Ninety percent (90%) of all hip and spinal fractures are related to osteoporosis. Among individuals now 50 years old, the lifetime risk of the any fracture in the hip, spine, or distal forearm is about 40% in Caucasion women and 13 % in Caucasian men. Two types of scores are used to quantify bone mineral density (BMD): The T score is the number of standard deviations the patient's BMD measurement is above or below the young-normal mean BMD. The Z score is the number of standard deviations the measurement is above or below the age-matched mean BMD. The World Health Organization (WHO) defines osteoporosis as a T score ≤ -2.5. © 2008 Springer Science+Business Media, LLC. © 2008 Springer-Verlag New York.