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My name is ***** ***** I have been a Vet tech for 30++ years. It sounds like the cat has pain in the leg, by the fact it has licked the hair off. The Vet can definitely treat the leg. The big issue would be determining the problem and the type of treatment needed. The treatment can range from setting the leg, to surgical repair of the injury to amputation of the leg if it cannot be repaired. As you can see the cat functions well on 3 legs, so whatever is done will help with the pain. The biggest drawback is if the cat is a feral cat, it will have to be kept in what the leg is being treated.
I hope this response is helpful.