Osteoporosis is a health problem where bones become weak and fragile. All through life, old bone is taken away by the body and new bone is added. Before age 30, more bone is added than taken away. This builds stronger, heavier bones. After age 30, more bone is taken away than is made. This can cause bones to become weak. Then, they are more likely to break. If your bones are just starting to weaken, it may be called osteopenia. The bones are less dense than they should be. This is not as bad as osteoporosis. Both of these conditions often happen without any signs. About half of all women older than 50 and about a fourth of men over 50 will break a bone because of osteoporosis.