Arthritis in cats been gaining a lot of focus in recent years. Historically cats were thought not to be subjected to the arthritic change we see in dogs, especially large breeds. However, very important studies have shown that this is not the case (simply proving what cat practitioners had known all along!) as 90% of cats over the age of 12 had documentable joint changes on x-ray even if they were not showing a lot of symptoms at home!
Some breeds of cats, like Main Coon Cats, are more at risk of developing types of arthritis, especially hip dysplasia.