Arthritis is a general medical term used to describe a disorder in which the smooth cartilagenous layer that lines a joint is lost, resulting in bone grinding on bone during joint movement. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In certain types of arthritis, other organs, such as the skin, are also affected. Onset can be gradual or sudden.