Apparently it's not always easy to know if a bone is actually broken. Some are more obvious than others.
In April 2006 I was transferring into the car when I heard a loud POP and my leg hurt really bad. It hurt again each time I moved it. My doctor sent me for an X-ray and MRI. I thought the X-ray would have been enough and the MRI was overkill.
The nurse told me everything was fine and I should go home, so I did. I was home less than half an hour when she called and said I had to go back. There was a fracture after all.
I always thought that was strange. Then I found an article on WebMD that says it may not be so strange after all. Sometimes an X-ray does not even show a fracture. Other tests such as an MRI or CT scan. I know the MRI simplified diagnosing MS and injured athletes often have MRIs, so I should not be surprised. The role of the MRI in diagnosing and identifying problems is expanding.
I was lucky they kept looking at my results after I left. Otherwise I would not have known my leg was actually broken and not merely bruised.