I wouldn't think they would all show swelling signs. Its good article touching on different disorders. I had a hen that did the penguin walk, I tried to figure it out, looking back she past some weird looking tissue, thought she passed remains of a mouse, she stopped laying, in six months, she was dead. The penguin walk look was just before she died. She was four years old i think at the time. When they get up there in age, stuff like this starts to happen.