I agree that aerobic exercise would be of benefit, particularly with the recent evidence of increased risk of heart disease in RA. However, I am not aware of any study showing the benefits of aerobic exercise in preventing radiographic damage.
Value of Aerobic Exercise for Rheumatoid Arthritis?
I have RA which is reasonably well controlled on sulphasalzine, prednisolone and methotrexate. I walk and swim but have heard that intensive aerobic exercise and gym work using a swiss exercise ball is very beneficial without radiological evidence of joint deterioration.