My sister commented as follows:
"I have both rheumatoid and osteo arthritis affecting my hands and other joints. I find the most important thing is to pace yourself. At the time it may seem fine to ring several times without a break, but you risk paying for it the next day(s). It's difficult in our tower as we hardly ever have enough ringers to take turns, but I've learnt to insist, so we have breaks and if necessary, shorten the practice sessions. I also refrain from ringing up and stick to the lighter bells. I find that rubbing in a bit of glycerin improves grip, so you don't have to grasp the rope so tightly, but some towers don't like that. I also tuck the end of the rope into a wristband (the stretchy cotton kind that sportspeople use). This is because I'm tall so I always have a long tail end which I hate having whisking around, but it does also give a degree of confidence if your grip is weak. Some folk say it's dangerous, but the rope would pull out in an emergency, and the worst you could suffer would be a rope burn."
I don't know whether this will help but it might. I encourage all ringers to relax their grip between strokes. Some people grip the rope the whole time but you don't need to between strokes when there's no tension in the rope,