Osteoarthritis of the base of the thumb is also known as trapeziometacarpal arthritis or carpometacarpal arthritis (CMCJ). In the early stages it can be helpful to strengthen the muscle between the thumb and the index finger. This can help because it actually stabilises the CMC joint, and can reduce the forces in the joint at rest, and when you pinch.
To do these exercises you can put a rubber band around your fingers and push out with the index finger and the little finger, against the rubber band. You will see the muscle between the thumb and the index finger contracting. This is called the first dorsal interosseous muscle, and keeping it strong could reduce your pain.
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