Hi! Feeby (17+ yo) was diagnosed years ago with arthritis, due to a limp in one of her front paws. She was on Glyci Flex Plus for over 3 years before she tired of it - and remained limp free the entire time! It contains glucosamine, chondroitin, green lipped mussels, MSM & DMG, I suspect the green lipped mussels is what she decided she no longer liked! Nonetheless, I would highly recommend trying it and maybe your cat will never tire of the taste! They are big chews, so it is best to break/cut them into 4 or 5 pieces for easier eating.
Other more basic products are Cosequin and Dasuquin. There are a whole host of supplements you could look at - just do an internet search on 'arthritis supplements' for cats.