It appears to be a slipped tendon. Treating it for splayed leg will not fix the problem. You have to manually work the tendon back into place and then secure it in place by making some type of brace or at least taping it in place. Slipped tendon (perosis) is often due to insufficient thiamine and niacin. Get a good vitamin B complex and make it up at the rate of 1/2 tablet or capsule to 1 gallon of water. Make this the only source of water and do not add anything else to the water. It will benefit all of your poults. The solution should be made fresh daily.