Sorry, I forgot to return and give an update on my RIR. She came down w/ what I believed was Marek's (exhibited most of the symptoms). I began treating her w/ hypericum perforatum after reading this thread. ( I found them at the Vitamin Shoppe if anyone has difficulty finding them).
I started treatment several days after finding her--took awhile to get the hypericum. She wasn't eating very much, if at all, and I would have to drop water into her mouth b/c she wouldn't drink. I wasn't sure she would make it but every morning when I checked on her she was still hanging in there.

One leg was paralyzed, had seized up, and wouldn't move. I worked at moving the leg and bending it (very slightly at first)----aka chicken physical therapy. It took a while but she finally did improve and began eating and drinking. She lost a lot of weight though. I would exercise her legs about 4x a day in the beginning and 3x later on as she improved.
She did get to a point where she got some energy back and would get up and move around. Her leg, at the bend, remained very swollen and she would hop around on the good leg. She began to put some pressure on the bad leg and I was hopeful she would eventually be able to walk on it again. After a couple of months, I moved her back down to a private coop where she could move around better. Her leg hasn't improved from where it was when she began to put pressure on it. She still hops around but moves around well given the circumstances. I keep her separated from the roosters b/c they try to breed her and I don't want further injury.
If you're treating a chicken, don't give up even if you don't see immediate results. As I said, many mornings I expected to find her deceased but she hung in there.
How long did you treat her with the Hypericum? There's something else that looks like Marek's but causes swelling in the joints...I just read about it recently but now I can't remember where. I think it might have been on Poultrypedia. Our pullet doesn't have any swelling at all. We have ordered another holistic treatment for her, and have decided to put her back on the Hypericum on half dose,until the other stuff arrives, as it will be a few days, and she has begun to decline again. WE are going to try Curcumin with Bioperene, but I couldn't find it in the health food stores, or vitamin shops, I had to order it.