Today's episode actually comes from a second opinion telemedicine visit with a runner who wanted to know more about a tarsal coalition. 

He had an X-ray and the doctor found this thing called a "C-sign." 

The "C-sign" is an abnormal appearance on an x-ray that suggests a tarsal coalition. When you look at the lateral view of the foot X-ray, a bridge of bone can form, partially encircling the talus bone and the calcaneus or the heel bone. It creates a bridging bright white thing that looks like the letter C on your X-ray.

A C-sign is abnormal, and it is one of the classic signs of a tarsal coalition. 

How can a tarsal coalition start causing pain in a runner? Well, that's a great question, and that's what we're talking about today on the Doc On The Run Podcast.