In general, foot and leg problems can be a result of any number of things. They can be genetic or result from: poor breeder nutrition, low incubation temperature, high incubation temperature, low humidity, high humidity, etc. Late hatching chicks, who probably had difficulty zipping in the first place, are most likely to show these symptoms. The best treatment is prevention: Make sure your breeders get the best nutrition possible, maintain the best incubation conditions possible, be sure that chicks do not spend any time on a slippery surface, and do not breed birds with foot or leg issues.
I had two major problems result from my last hatch. One resolved itself beautifully, and the other did not. One chick had crooked toes and the other had a slipped tendon, also called perosis. Gail Damerow attributes crooked toes to low incubation humidity, cold brooder floor, zinc deficiency, or heredity in her Chicken Health Handbook. Slipped tendon is caused by calcium/phosphorus, manganese, or other vitamin deficiency (biotin, choline, folic acid, nicotinic acid, or pyridoxine.)
There are two similar conditions. Curled-toe paralysis results from severely undernourished breeders. Chicks walk on the tops of their feet and often die after a few weeks. Splayed legs, where legs are spread out to the sides, results from slippery brooder flooring.
I treated my crooked toes by making sticky shoes to hold her toes in place. I cut pieces of bandaid or clear tape (easier to see what I was doing) about an inch long. I laid one piece of tape on the top of her foot, used my finger nails (some use tweezers) to gently move and bend her toes until they were straight and spread, and pressed them into the tape. I put another piece of tape on the other side of her foot, squeezed the tape to touch between her toes, and trimmed around her foot. I changed her “sneakers” every day, and by the 4th day, she was fine.
My other chick had a slipped tendon. This means that the tendon was not in the groove where it belonged. Eventually, the bottom part of his leg, below his hock joint or “knee,” was essentially twisted sideways, almost backwards. He could not walk, only crawl short distances on his stomach. At first, I was able to pull his leg straight, but the hock joint became swollen and probably infected over time. It leaked some blood and pus at night, and I was unable to help my chick. It was awful for us both, and I hope that, if this ever happens to one of my chicks again, that I will be better able to rehabilitate him.
Because it was a nutritional problem and he could not walk to eat or drink, I fed him water with vitamins and minerals and baby parrot feed every hour or two. I put a “hobble” on his legs to try and hold them together and set him in a cup to keep his legs under him and keep him from being trampled in the brooder. Later, I made him a paper cup with a fabric seat with two holes cut for his legs, sort of like a baby’s bouncer. The idea was to have his legs down and touching the ground so that he could exercise them. I also exercised and stretched his legs after each time he ate: I stretched his legs out and also moved them in little circles like he was riding a bicycle. I put triple antibiotic ointment on the bleeding areas of the swollen hock. I think now that I should have also fed him water with asprin to bring down the swelling in his joint so that I could push it back into place more often. I still wonder what more I could have done. Usually, though, if the joint becomes infected, there is nothing more to do. We had to put him down, and I am really too upset about it still to talk about it.
Anytime I had to work on their feet, they did not appreciate being held. So, I figured out a way to keep them calm and unstressed so that I could work and have both of my hands free. I placed a hand towel on the floor, folded in half. Then, I put the chick, belly down, in between the layers of towel. They snuggle right in. I then held them down with my left hand, gently pull out the leg I need, and do my work. I usually have to hold the “thigh” bone between my left thumb and index finger while putting on the shoes, hobble, or other device with my right hand. This worked really well for putting on and taking off leg bands as well.
There is a ton of information on how to deal with these conditions. The best is Poultry Podiatry (I also like the older version of this page) which covers a full range of conditions and treatments. Other useful links are: