Osteoporosis is a disease marked by reduced bone strength leading to an increased risk of fractures, or broken bones. Bone strength has two main features: bone mass (amount of bone) and bone quality. Osteoporosis is the major underlying cause of fractures in postmenopausal women and the elderly.
Click here for more information. http://www.niams.nih.gov/Health_Info/Osteoporosis/default.asp