interesting, I have been having pain in my right thumb, it seems to be in the joint area, I have a road bike, I use my thumb to shift the gears but I think it may be more about braking not shifting, I mainly use my back brake to slow and both to stop, seems holding that back brake is the culprit, I just don't know what to do to "fix" the problem

I am trying to remember to use the front brake more, I just don't want to end up with both thumbs sore.