We have another kitty that has a knee issue too. It comes out of joint. But that is from an injury he had when he was little. His femur was broke. Someone kicked him (before he was rescued) his knee has never been the same. He has to keep his weight down as well. He has the cutest hitch in his walk and run though. And he is very strong in the shoulder's because of it. Sometimes he can't jump all the way onto a counter and has to pull himself up. poor boy.