Arthritis patients should avoid repetitive movements (typing on a keyboard, operating certain machinery, and so on) and static postures (sitting or standing for long periods of time). These motions will put strain on the joints you’re using to do the activity or to maintain the position. If you must do repetitive movements, it’s a good idea to move or change positions often to avoid stiffness, and stretch and relax often. Ask a physiotherapist to recommend specific stretches for the task you are doing.
(Source: Koehn, C., Palmer, T., Esdaile, J. Rheumatoid Arthritis Plan to Win. Oxford University Press. Oxford: 2002.)