If we live long enough, we all get arthritis -- even cats. They try very hard not to show pain, but if your senior cat is hiding, not eating, drinking a lot and losing weight, she's hurting and needs your help.
Consult your vet for pain medications. This is a touchy issue with cats, since many of the drugs that work in other species, such as horses and dogs, are dangerous for cats. Aspirin is relatively safe at low doses for some cats, but doesn't work for others. Buprenorphine can be helpful and bypasses the digestive system altogether -- you paint the liquid onto the cat's gums. As a last resort, steroids can be beneficial enough to outweigh the long-term issues they can cause. Be sure to ask about nutritional supplements such as glucosamine and chondroitin -- some vets endorse them, others not so much.
Provide warm, soft places to curl up in sunny, draft-free places that are easy for your cat to get to -- she'll show you where she likes to be. Consider providing a heat-reflecting bed that conserves the cat's own body warmth. You can use a heating pad on a low setting, but only when you are present and monitoring.
A Little to the Left, Please
Help your cat with her personal grooming with daily brushing, with special emphasis on any areas that may get matted or unkempt because they're hard for her to reach. Check her ... um ... personal zone to be sure she is clean there. If she's not using her scratching post, her claws may grow too long and need trimming. If she'll allow it, give her some gentle massage over stiff joints and even some range-of-motion exercises.
A Little Lift
Keep everything -- food, water, litter box -- on one level for easy access. Find, modify or make a low-sided litter box she doesn't have to step high to get into, and surround it with newspaper or a washable rug in case she just can't make it. Try a softer litter in the box if her feet are sore. Provide pet steps, low tables or even boxes to make it easier to get up on furniture or other favorite perches. If you sleep upstairs and she does, too, carry her up. Look for a lightweight cat flap that's easier to push open and won't press on her so hard when it comes back down; if necessary, make one or tie up a corner of your regular one for easier access.
Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.