For people with rheumatoid arthritis, when the joints are warm and swollen, rest will help to settle the disease down. At times like this it is necessary to rest more, to do less unnecessary walking, participate in fewer activities, etc. Though reducing activity, you should still maintain joint mobility by doing range-of-motion exercises. These are light exercises, done without any weights and designed to preserve the mobility in the painful joint. The joint should be taken through a full range of motion each day, paying special attention to the end of the motion where the mobility is lost. Ease the joint fully to the limit of range. Aquatic exercise usually can be continued at these times as the buoyancy of the water protects the joints from rapid or stressful movement.
(Source: University of Washington, Orthopedics and Sports Medicine)