not with severe RA (referring to the amount of joint deformity) but with less severe cases sure you can as long as there are no other contraindications. in fact if the joint is tight i'd highly suggest it. as always, have the do something painful (perhaps walking or raising an arm) and then mobilize them. if they repeat the movement and there is improved ROM or pain then you have shown it to be helpful. however, if mobilization doesn't help then stop.