It’s a degenerative condition that affects and inflames one or more joints. It can result in changes to the joint cartilage, joint fluid, joint bones and capsule of the joint, making them stiff and/or painful. If your dog has arthritis, he or she may have difficulty sitting or standing, or be reluctant to jump, run or climb stairs, or they may sleep more. They may seem generally slower or stiffer and show less interest in play, and you may even see behavioural changes such as anxiety or aggression. Their decreased activity levels may result in visible weight gain.