I posted this at my cat forum but I have only received one reply so I am pasting it here as well:
My kittie was on her cat tree the other day. I am not exactly sure what happened, I just saw the tail end of it, but I heard a noise and she had fallen I guess coming down and was hanging on the middle part trying to get back up. I ran over to her, but she had already scrambled to the middle platform before I could get to her. She made a noise when she fell, but I could not tell if it was a "that scared me" noise or a "I got hurt" noise. She held up her left paw (which is the one she had caught herself with on the cat tree) like it was hurt. I went over a looked at it and it looked ok and then right away she started walking on it and running up the stairs and stuff, so I assumed it just scared her. This was on Thursday. Since then she has been walking on it fine. Until today. Now she is hobbling around and won't put pressure on it. I softly pressed the pads on that foot and she didn't cry or anything and my hubby checked each nail to make sure none had been ripped out when she caught herself and they were all there. I was looking on the cat tree and I found where it looked like a stripped part of a nail, but it looked like the ones I find when she uses her tree scratching post, but it was a little bigger. What do you think? And don't worry, I have been thinking vet, vet, vet all night.