One of our chickens has a broken leg. A few months ago the neighbor's dog attacked her. She drags it around and never uses it. We kept an eye on her and found that she was still eating and drinking fine. Here we are months later and she still doesn't use the leg. She lays in one spot all day except to eat and drink. She is quite dirty in her own droppings. Our biggest concern is that she would bring disease to the other birds. Should we put her down?