Low energy and low activity
You could realize that your cat has less energy or capacity for pleasurable activities like playing with toys or chasing that red dot. Your cat may be afraid to jump, walk up and down stairs, struggle to get up from a laying down position, be restless, and have trouble finding a comfortable place to rest. Changes in sleeping patterns are also possible—the cat may sleep more or less, and in unexpected positions and places.
Changes in the litter box
Because of the pain associated with going in and out of the litter box, as well as difficulty sitting, cats frequently miss their litter boxes. A cat with sore hips or knees may find it difficult to maintain the sitting position. Due to the pain and urgency associated with other physical issues, cats may refuse to use the litter box.