Do you have a (very) warm water pool with a shallow area where you live? I have read on the website of the Arthritis foundation that walking in water is the safest form of exercise for this condition. There is such a pool within a 30 minute drive from me and I sometimes go. I do not have arthritis (not yet, as we will all be there), but I simply love walking in water. And I usually walk sideways and backwards, not forwards, and this way I exercise muscles that I cannot exercise on land.