I'm pretty surprised that nothing showed up on the bone scan, but you wouldn't expect the oedema to show up on a CT scan. Perhaps you've caught the problem too early even for a bone scan. The doctor seems to know his stuff. The reason for putting him in a brace is that even though there isn't a fracture now, there could be one in a few weeks. It is very possible that the situation will get worse before it gets better (I hope that isn't the case.) so the brace is a wise precaution. The first step that the body takes in healing a bone injury is to clear away the damaged bone. That happens well before the body starts building new bone to replace the damaged bone. As a result when there is a sudden increase in activity a stress fracture can result even after the offending activity has been halted.