My cat is about 2 years old, she's ridiculously curious and jumps off of all kinds of various locations. She was at a friend's who was watching her for awhile and may have jumped off something and hurt herself, or maybe not; we don't actually know. She is not in pain, but when she walks it's a bit weird: she is taking baby steps with both her back legs instead of full strides and when I pet her she normally kneads with all four paws, but now will only use her front two. She doesn't appear to care, there is no swelling, heat or painful spots anywhere.
Apparently, it was quite a bit worse when she was found that way late last night. The vet technician, who was looking after her, took her to the vet this morning and he examined her and then, once again around noon with me being there, and said she was moving better than even this morning. I got her home with me, she's not very happy that I won't let her roam around, but she has always been a good cat and after some convincing, she was willing to simply lay down on me. She's happy to eat treats or food and purrs as loud as she can if given attention. The vet suggested that I lock her in a cage so she can't move around, but she's much happier laying on me or beside me on the couch than in a kennel. She has no problem moving her paws and can move the legs when she cleans herself, but seems to not move them if she can help it.
The vet has no idea whats wrong with her, but said she has no neurological symptoms, signs of pain, swelling or fever. He didn't even want to give her an anti-inflammatory, what could possibly be wrong with her?
She's a ragdoll in case that's relevant, she also likes to flail her tail around when she's overexcited or becomes impatient with me. If given enough pets, she will still happily thrash her tail around and move her back legs. The stiffness only seems to be evident when walking or attempting to climb something.