I would rule out things, treat her worms and mites, give her vitamins. Click on the link I previously posted and eliminate what you can and hope for the best. She can be weakened by just having these.
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...
Unfortunately it could be anything. Egg-bound is my first thought, she could be vitamin deficiency, Marek's disease, rickets, coccidiosis. Worm her and treat her for mites. Rule out things. Bring her into the house to keep her warm, see what her poop looks like.
Here is a link that has...