Can osteoporosis be diagnosed by regular x-rays?
Often patients are told that they have osteoporosis based on an x-ray or after a surgical procedure on their bone. Unfortunately, these statements are misleading, because the only way to accurately make the diagnosis of osteoporosis is with a bone density test.
Your doctor may be able to tell you your bone "felt weak" at the time of surgery or "looks thin" on a regular x-ray, but the diagnosis of osteoporosis has strict criteria that can only be made with a bone density test. If there are concerns that you may have osteoporosis because of the appearance of bone on x-ray or an injury that you sustained, you should ask if you need a bone density test.
Sources:
JM Lane and M Nydick "Osteoporosis: current modes of prevention and treatment" J. Am. Acad. Ortho. Surg., Jan 1999; 7: 19 - 31.

