My horse has had some sensitivity over gravel and rocky surfaces that became noticeable when I really started working outside of the arena and off beach sand on a regular basis. I posted a thread that Loosie responded to several weeks ago (thanks!) that his back feed looked funny, where there was a ridge at the front of the sole that was separate from the hoof wall at the toe, but I could never get a good picture. Farrier plan was for him to come out and try shoes all around rather than just the fronts. When he got there, he said that the issue making his hinds look odd was actually a retracted sole, and that it might account for his soreness. He said that there's not a lot really known about retracted soles. My horse has shoes all around now and went completely sound over gravel immediately after my farrier trimmed and shod him and has stayed that way.
Have you all heard of retracted sole before? Is it something that may become an ongoing or recurrent issue? Causes? Anything I should do to help him out? Any resources to learn more? Google wasn't a lot of help for me when I looked.