Kitty knuckling on 1 rear leg

I noticed before I left for work this morning, 6am, that one of my cats was limping on his right rear leg. I just got home and he is not so much limping but knuckling. It is just that leg, he is not crying, he is eating, being social, and walking around. Does not seem to be in any distress at all. In my experience, if he had thrown a clot, saddle thrombus, it would effect both rear legs and they are more paralyzed. It is also very painful. Can anyone enlighten me as to what may be going on or if I need to go to the emergency pet er? He is not hyperthyroid. He does have IBD and is being treated by an internal medicine specialist. His bloodwork is normal and was done less than a month ago. Advice?

I can't help you much with what it is, whether a sprain or strain.  I wouldnt rush to the emergency vet for it but would get him checked at your regular vet if it persists for a day or gets worse.

Having just lost a cat to saddle thrombus, I would say it isn't that.  My cat was instantly paralyzed in the hind legs and screaming in pain, and her tail and feet were cold.  By the time I got her to the vet the paralysis was working its way up to the front legs and we put her to sleep as quickly as possible.  I was glad I had one dose of buprenex in the house to give her immediately, so by the time we were in the car on the way to the vet, she had stopped screaming although I'm sure she was still in pain. That just helped.  I have never heard of saddle thrombus doing just one leg, but a small blood clot COULD do just one leg, so if the foot feels cold, or the cat starts showing signs of pain, THEN rush to the emergency vet.

Thank you for your reply to Preston's injury. I have spoken with my vet and lucky I do work in a specialty veterinary practice, so he is seeing the neurologist tomorrow. The knuckling has gotten a little worse even though I have confined him to 1 floor of the house. No stairs but he is still jumping on sofa and kitchen table. Still no signs of being painful, It has not stopped him from wondering around and being social, still e/d normally. We will see tomorrow. Thanks again, I will post what the neurologist says tomorrow, his internal medicine specialist recommended neuro consult.

Just got back from the neurologist with Preston. Sadly, he has been diagnosed with spinal lymphoma. On to the oncologist tomorrow.