It is pretty easy to fix as a chick but I have not tried as an adult. Seems like that would be tough because they are not as flexible. I got some pure Ameraucanas from a lady In Montana and they all had crooked toes...that was another story, not a happy camper because they were ordered as adult birds and given to me in a box, did not notice the toes, after driving hours to get back home I realized the toes were all messed up and she said she thought it happened on the ride home....ummmm, what? Did not get birds there after that, despite the pretty blue eggs, I found someone a little closer. I believe that was a genetic issue. A guy in Idaho falls also got some with crooked toes from the same place
I was sure not to use them for any sort of breeding llike RJ said...just not good chicken husbandry to mess with those as breeding stock.