REtraining my cat to use his liter box

Question
Dear Dr. Gotthelf,

My three year old spayed cat has stopped using his liter box and I was told to retrain him to use it. Do you have any information on how to do that?

THANKS,
ROSE KONOWALSKI

Answer
Sometimes it is the litter itself that is the problem.  Sometimes it is too dusty or has an objectionable odor.  Sometimes it is the location of the litterbox.  And sometimes it is that the cat may have an arthritic problem that prevents the cat from jumping into the litterbox.