I'm not sure about the "permanently disabled" part, but in other cases they look at whether or not you can perform the work of your last job, if you can't, then they look at if you can perform any other type of work in the national economy.

So just because you can't lift heavy objects, doesn't mean they can't deny you because you're capable of sitting at a desk doing work. It's your job (and that of your attorney) to prove you can't do anything.