We went through this with one of our OEG roos. One minute he was fine and the next he could not walk. With a bit of therapy we got him to where he could walk like a penguin. As time went on he got worse and worse and I finally had to put him down after about 4 months. We thought at first that it was an injury but was able to rule that out. I looked everywhere for an answer and after ruling out many different things came up with what is called "Salpingitis". It is an oviduct or vent infection that is caused by E Coli. It moves up into the inner systems of the chicken causing all sorts of problems, one of which is partial paralisis hench the walking like a penguin. Most people think "Egg Bound" when a chicken displays this characterization but that is kind of hard when it is a rooster. I could never find any type of cure for this disease.
Keep us posted...
