X-rays are electromagnetic radiation of shorter wavelength than the light seen with the eye. X-rays are produced when electrons travel at high speed and strike certain materials such as heavy metals. They can also go through bone onto photographic film. This leaves a picture that can be examined for fractures and other problems.

A fracture shows up on an X-ray because the bone has been disrupted and no emission passes through that spot. In the case of a stress fracture, or a reaction of the bone to repetitive motions, there may not be enough damage to show up on an X-ray.

In this case, a bone scan may be used. With a bone scan, a radioactive substance is injected to produce images of the bone. The radiation shows up in the bone in varying amounts. Areas of increased activity are called "hot spots." These are seen where bone growth from a tumor, fracture, or other stress on the bone has occurred.