Arthritis means inflammation of the joints. There are many forms of arthritis. People most commonly think of old age degenerative arthritis, where a joint becomes warn and stiff due to a lifetime of use, but arthritis can also occur due to damage from trauma such as a fall or accident, damage due to a badly aligned joint such as that seen in dogs with hip dysplasia, or in some cases due to infection.
Any cat with joint pain or stiffness is very likely to have a degree of arthritis occurring. As arthritis progresses, the healthy smooth lubricated joint surface becomes roughened and irritated, causing further scratching and irritation and worsening the problem. For this reason, it is vital to control this before the arthritic inflammation causes permanent damage.
Any cause of joint inflammation and arthritis should be controlled with a combination of rest or reduced exercise, joint supplements including glucosamine and Omega 3 and in some cases medical treatment.