My 11 yo cat suddenly started limping two weeks ago. She doesn't want to bear any weight on her left hind leg, but I also think she may be a little down in her back. Hard to tell with cats, though. There has been no swelling. My vet did a physical exam and didn't find anything wrong, but she wouldn't walk for him. She only slinked around, so he couldn't see her limping. He tried to feel for any swelling anywhere on her legs, but there wasn't any. After my insistence that something is causing her very significant pain, he gave her a round of steroids. After two days, I've seen zero improvement.

She growls when she tries to scratch her ear, she constantly shifts from side to side laying down, all the while growling or meowing (I assume in pain), and she isn't carrying the leg, but will only put enough weight on it to barely hop. When she's standing still, she holds it up. Sometimes when she's laying down, she stretches it out totally straight. Rather than sit like a normal cat, she holds herself up with front feet and has her back end laying on the hip (either side).

I really need some ideas. The vet offered none. She's in pain most of the time. I can see her breathing getting heavier when she moves, and she just never looks comfortable. She's a house cat (never goes out), but the other cat does fight with her sometimes. I'm thinking this is some sort of injury, maybe even twisted her back (?), but I thought it would have improved by now. If anything, it is somewhat worse. Ideas?