So I took the poor baby into the vet (she wet herself, as usual, that was just a Very Bad Day for kitty). The vet suggested and got her x-rayed to make sure nothing was fractured, and found nothing wrong, can't find any sign of bites or damage apart from a tiny bit of swelling. He's guessing a sprained knee. She's 10, still thinks she's a kitten. Anyone can hop off of something high and land wrong, which was his guess.
He recommended keeping her resting in one place and not let her jump on anything -- keep her in a cage if need be. That would help her heal. I asked how long, because she panics when I lock her up! He said, "oh, several days."
So I was trying to think what to do. But when I got home she just went straight back to the walk-in closet, and she's a little more herself now, but she's not coming out, no way charlie! She's found herself a cozy corner. I put food and water in there with her, and the box happens to be right next to the closet anyway, so she's all set.
She seems a little better today, she's purring and relaxed when I go to check on her. She's just staying tucked out of sight until it stops hurting. The vet gave her antibiotics and a shot for the pain and inflammation.
Poor kitty. I think she'll be fine, and I'll be watching to make sure she comes out of there in a few days and starts walking again, but a hurt little animal is such a sad thing!
And such a ham when she's healthy.