He also is walking a little strange. When he walks casually his hind legs are stiff. However, when he's startled he has no problem taking off. He can jump up and down fine and his appetite is normal. I noticed it today and I'm wondering if he hurt himself while I was at work. He's an indoor cat. I'm thinking of monitoring him closely the next couple of days and then see how he's doing before taking him to the vet. Any suggestions?