http://orthoinfo.aaos.org/brochure/thr_report.cfm?Thread_ID=13&topcategory=Osteoporosis
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American Academy of Orthopaedic Surgeons
Osteoporosis is a disease of progressive bone loss associated with an increased risk of fractures. It literally means porous bone. The disease often develops unnoticed over many years, with no symptoms or discomfort, until a fracture occurs. Osteoporosis often causes a loss of height and dowager's hump (a severely rounded upper back).