http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=87&topcategory=General%20Information
American Academy of Orthopaedic Surgeons
Osteoporosis causes bones to thin and weaken. With osteoporosis, bone minerals (mainly calcium) are lost, causing bones to become so brittle that they could result in a wrist, hip or spine fracture. No matter what your age, you can take steps to prevent bone loss. This document provides some preventative tips developed by the American Academy of Orthopaedic Surgeons that you should follow during the stages of your life.