I had an occurrence of this a couple yrs ago in my left hand and it's sounds a lot like what you're experiencing. It sounds like De Quervains tendinitis. I went through anti-inflamitories, a brace for 5 months and 2 cortisone shots to the joint. Finally, a yr later had surgery to solve the problem. Here's a link to a good explanation: http://orthoinfo.aaos.org/topic.cfm?topic=a00007 They sliced away the synovium on mine because the tendon was so inflamed it wouldn't slide through. No problem since...