I had this problem last fall - I developed tendonitis in my left wrist from knitting. I've changed my practices and am a much healthier knitter now. Things I've done which have helped:
1. I almost always knit on circular needles instead of straight needles. This helps take the weight off my hands and wrists.
2. I take frequent breaks, especially if I feel even the smallest of twinges.
3. I stretch out my hands, wrists, and arms a lot.
4. I sit up straight, with good back support, and keep my arms close to my sides while I knit.
5. I also took B6 and glucosamine for a while when I was recovering - I'm assuming it helped.
I started a topic for this issue a while back - it can be found here: https://www.craftster.org/forum/index.php?topic=11957.0
- the article by Bonne Marie Burns on Knitty really helped me.
Hope you feel completely better soon, Roe!