Why would an older cat suddenly stop defacating in the litter box?

My cat has always been great about using his litter box, but one day decided he would only pee in it. Now he poops on the basement floor (not far from the box). I know cats often stop using their boxes when they are facing health issues, but if this were the case, wouldn't he abandon it altogether? It's not a huge deal, as he only uses the cement floor and it's as easy to clean up as if it were in the box, but I'm just curious about the behavior. Thanks for reading!

 

Have you changed kitty litters at all? Or are you keeping it clean enough? It's actually possible that you should replace the box itself (if you've had it a few years, it probably has soaked in the smell). I know it's weird he's picking and choosing what he does there, but I've seen it before unfortunately.

 

My older cat (she was around 15 years old) would do that when her joints were hurting and she couldn't step over the box. She just started going around it. Check to see if he has arthritis by taking your cat to the vet.