Switching to a vertical mouse cleared up my arm pain. I tried many vertical mice. Evoluent's wired vertical mouse has been my favorite since 2009. Each new version is essentially the same, just with different surface finishes.
Years later, I got wrist pain in both hands. Switching to a tenting keyboard solved it. I've used the GoldTouch V2 for 7 years now.
Do not try 3M's vertical mouse with the thumb button. I used it for a few months and developed severe pain in my thumb. Fifteen years have passed and my thumb still occasionally clicks when I bend it, due to that injury.
Years later, I got wrist pain in both hands. Switching to a tenting keyboard solved it. I've used the GoldTouch V2 for 7 years now.
Do not try 3M's vertical mouse with the thumb button. I used it for a few months and developed severe pain in my thumb. Fifteen years have passed and my thumb still occasionally clicks when I bend it, due to that injury.