I'm taking my cat to the vet once they open up. I came home yesterday and there was clearly something wrong with one of his legs. He ate a bit and wasn't vocalizing any distress, so I went along with what I read on the internet about how it might be a sprain and how it wouldn't be a terrible thing to wait until morning rather than making an emergency visit to the vet. Little dude is not improving at all though. Instead, he seems to be struggling to stand up at all now. I adopted him as an adult, so I don't know exactly how old he is. But it should be somewhere in the 15-17 years old range. I'm terribly worried about him.