Welcome to BYC and sorry about your chicken. Some of the problems with your chicken may have to do with heredity, mineral deficiency in the parents, or hatching temperatures. Feeding a good balance and fresh feed and alowing them to free range and nibble on things in their environment is the best thing you can do. Only hatch the best eggs from the best chickens. Don’t hatch eggs from chickens who have defects. I agree with letting your chicken have the best chance to survive, even with a bum leg. Some do okay in small flocks, but if they are being picked on or starving, it is best to help stop suffering. Good luck.That's sad. But I suppose part of raising chickens. I just found one of my chicks with a leg like that. I thought it might be dislocated or broken. But after reading this I think it may be more complicated. Provided it can get around and doesn't look to be in to much pain I am going to let it grow up. In general if the chicken is eating and drinking I give it a chance. I will probably take it to Disneyland earlier than I would have otherwise.
This along with a beak deformity in a previous batch of chicks has led me to switch back to a local brand of organic feed.