Arthritis is where you have an inflammation of the joints. And in old age for dogs it means that the joints swell and become painful and stiff. Some of the things that can cause this problem are earlier injuries such as torn ligaments. Symptoms of arthritis are lameness particularly after first getting up from lying down and unwillingness to jump or go for long walks or even getting up. Dogs will suffer more in winter time as the joints tend to swell more.