Good news. Like people, cats are living longer lives -- and as cats age, they run into the same kinds of health issues older people do, including arthritis. Stiff and achy joints can make it difficult for older cats to use their litter pans, but don't despair. There are things you can do to make it easier for your mature cat to comfortably use its box.
Litter Box 101
Emily Levine, DVM, and an animal behavior resident of the Animal Behavior Clinic at Cornell University College of Veterinary Medicine says, "We remember to give medications, but we tend to forget about addressing food, water and litter box issues." Indeed, the normal litter pan may no longer be suitable for the older cat, especially if the sides of the box are high, making it difficult for your cat to step into.
A Box on Each Level
Besides arthritis, older cats can develop bladder and bowel control issues, so it's a wise idea to have litter boxes on each level of your home to make it easier for kitty to find and use the box. Remember, too: Some cats with arthritis may have achy joints that prohibit them from climbing up and down stairs to get to the floor where the box is located. Best to provide one box per kitty per home.
The more difficult it is for the older cat to get to his box, the more likely he may not use it. Some cats with arthritis or other health issues may "think outside the box," using the litter box only when it's convenient for them, so it's best to put the box in a place that gives him privacy but is easy to reach (not next to noisy or heat-producing appliances or your cat's food bowls).
Changing the Pan Plan
Sometimes older cats use the litter pan only when they need to urinate, doing "No. 2" elsewhere -- often in an inappropriate place in the house. If this is the case, you might try using a low-sided litter pan, such as a large cookie sheet, to encourage your kitty to do its duty in the appropriate place -- the pan (box). You also might put plenty of newspapers around the box in case your cat has an accident.
There are plenty of alternative, often expensive, boxes on the market -- some have covers with charcoal filters to wick away odors, others have automatic scooping devices -- but most of their innovations are for the owner's convenience, not the cat's. In fact, the cat may dislike such complications. A simple plastic box with unscented clay and a scoop is all that's needed. Always keep the box as clean as possible, even if it means scooping several times a day.
If your arthritic cat cannot climb into the box, you might try to cut down the front side of the box to make it easier for him to climb into (just be careful as you cut through plastic). Another option is to scatter doggie pads, which are like newspaper but more absorbing, around the litter boxes. Finally, be careful of how much litter you use. Only one-quarter to three-quarters of sand is necessary to fill the box.