Properly using heat and cold treatments can be very helpful in comforting the pain and stiffness of arthritis. Cold packs work by numbing the sore area and reducing inflammation and swelling. This treatment is especially good for joint pain caused by a flare. Heat treatment from heating pads or a warm bath helps relax your muscles and promotes improved circulation. After using heat or cold treatments check the area for skin damage such as purplish-red skin or hives, this may indicate too strong a treatment. Next, move your joint to reduce stiffness and always let your skin return to normal temperature and color before using heat and cold again.
(Source: Arthritis Foundation)