X-rays are unable to quantitate bone mineral density. It takes about 30% bone loss before a standard x-ray is able to detect low bone density. Therefore, x-rays are not used to assess bone density and risk of fracture.
However, x-rays are used to diagnose broken bones. When a fracture is suspected but not obvious such as a stress fracture, further testing with a bone scan using nuclear medicine or an MRI may be ordered.