I used a Calcomp 16 button cordless digitizer for many years...I used to joke that the only thing that ever got exercise was my three middle fingers on my right hand...and now I find myself changing up and doing other things because of the pain in my fingers on my right hand....I still have not yet tried switching to the left... and I am reluctant to even think about it, but it might just be the only option in a few more years...
Mine was a Summasketch with the 12 button puck. The pain started in the back of my right hand one Wednesday morning, by Friday night my forearm was noticably swollen. Then everything went back to normal over the weekend and stayed okay until Wed. again. This cycle lasted about 6 weeks getting a little worse and happening a little sooner each time. Then we hit a crunch and I was putting in 16 hour days for a couple weeks with no weekends off. By the end of the 2nd week I couldn't close my right hand.
The tendon was swollen 3 times it's size and the doc said it was toast. He'd never seen an MRI like it before, apparently there were irrepairable stess fissures length-wise completely through the tendon. That was over 8 years ago and I still can't use my right index finger on a mouse for more than a few minutes without a couple hours of pain.