When are x-rays useful for runners with Morton’s neuroma?

Let's say you're out on a run and you start getting some aching pain in the ball of the foot. It persists for a while. 
 
It's not really that bad. Your foot is not killing you. But it starts to bother you more and more over the course of a few weeks. 
 
Being proactive, you see a podiatrist. The podiatrist tells you that he thinks you have something called a Morton's neuroma. So he does an x-ray of your foot and what do you see? Well, nothing. Why is that?
 
When are x-rays useful for a runner with a Morton's neuroma? 
 
Well, that's what we're talking about today on the Doc On The Run Podcast.