Arthritic chicken? Update-walking like penguin.

[CinnamonQueen12]

I have a black australorp that has been acting strange. It all started back in October when she became exessively broody-wouldn't get up to eat, drink, stretch, anything. Eventually, we broke her broodiness, but by that time, she had lost so much weight. Then, she started walking funny, with her tail down and her back straight, kind of like a penguin walks upright. And she was taking these little baby steps. We took her to the vet, who said she had this disease that causes a buildup of gas in the stomach. She was treated and cured. But now, she's walking upright again, exept her tail isn't down, but its not up, either. She's taking small steps, too, almost like it hurts, and it gets worse when she's out in the cold. Could it be arthritis? Her legs and knees aren't swollen, but why would she be holding herself completely upright when she walks? Any ideas?

UPDATE- Ever since she was sick in october, we had kept her inside, since she relapsed the first time we brought her out. Today is nice and warm, so I brought her outside, and withing 20 minutes, she was doing this penguin walk that she did the first two times she was sick. Her tail is down, she wont open one eye, and all she wants to do is sleep. When she does walk, her feet are close together and she takes slow, small steps like each one hurts. I found posts on here about ascites, but she doesn't have the "balloon" of fluid on her bum. Does anyone know what is wrong with her?