The above advice (Kaleea) is very good. I also have mild arthritis in the thumb of my left hand. I play fiddle as well as guitar and recently experienced pain in my wrist and thumb. I had physical therapy for the past several weeks - my PT was also a guitar player. Stretching, heat and cold treatments, and muscle strengthing were part of the regime. Also an X-ray confirmed the mildly arthritic thumb joint. Now it is much improved, but I have to recognize the limitations in my wrist and hand movement and avoid any extremes that elicit pain. Also avoid overuse, and use a cold pack after practice if pain appears. Later, heat improves the circulation and healing. You really have to learn to live with these limitations and not push to extremes. I'm now much better and can play without pain if I don't push it.

Good luck. See uour doctor and work with a good physical therapist.

Cheers, S. in Seattle