Bones are in a constant state of change—remodeling themselves to withstand the stress and strain of daily activity. In osteoporosis, natural bone activity becomes impaired, resulting in excessive bone loss. Bones become thin, weak, and more susceptible to fracture. As many as 10 million Americans have osteoporosis. Each year in the United States this condition contributes to approximately 329 000 hip fractures. A broken hip can cause discomfort, promote disability, and result in loss of independence. The loss of activity may likewise contribute to back pain and spinal deformity along with a loss of physical fitness and muscle strength. The November 28, 2007, issue of JAMA includes an article that examines various factors associated with a higher risk of osteoporotic fracture in older women and men.