Stress Fracture



I posted a while ago about easy child and his swollen ankles. Actually ankles/shins. He started working out about 6 months ago. Running is a big part of his workout. First we blew it off as shin splints. then the swelling went to his feet and he couldn't get his shoes on. couldn't squat (for work) it was too painful. Went to doctor., had x-rays, blood work..All fine. then noticed that he had no arches. (he did when he was little)
I made an appointment for him to see a podiatrist, thinking this had to do with his arches.
He went today. doctor told him there is significant "fallen arches" however he didn't feel that was the problem. it would aggrivate the issue, but he felt it is Stress Fractures. Wants him to have a bone scan.
I tried looking it up online, I was under the impression that "stress fractures" were not actual fractures. I am confused as it doesn't quite say one way or the other. Is it a real fracture? Or is it just from overuse?

any experience?