im not too sure about knuckles but i know that for fingers, they dont put a cast on as such, just a metal thing that immobilises your finger so they may use something like that. As for the wrist, it depends on whether you mean your actual wrist (eg your carpal bones) or your forearm. Your forearm gets put in your usual fibreglass or plaster cast. If its your carpal bone you may not need a cast because they are cubiodal bones, not long bones. A cast is designed to keep your bones aligned correctly so they can heal properly but the carpal bones dont need to be realigned. I fractured the head of my radius recently and because I had besically just chipped of part of the bone, the bone didnt need to be realigned and they didnt put it in a cast.
