I've looked at a few knitting forums and noticed all of them have a thread about hand or wrist pain. I can't knit lately because of my hand pain. I've also overused the computer and made my wrist hurt even more. I saw an orthopedic dr a few years ago about my hand and wrist. Not a whole lot of help.
Knitting too long can bring on the pain. The "one more row that's all" that ends up being ten rows when I know my hand is signalling me to stop now or pay later always ends in disaster and several days away from knitting. Know when to stop.
Most sites say to use circular knitting needles. This does help but pay attention to the yarn and the needles together. I was using a fuzzy acrylic yarn once that dragged on my bamboo needles and caused hand strain. The same yarn on my Denise needles was fine.
Many people will say to change my knitting style. Easier said than done. I normally knit English style; I can knit continental but not well yet. When I tried continental it made my left hand hurt. I haven't given up though. I try not to attempt new things when my hand is hurting because I tend to tighten up my hands when trying the new stitches which, of course, makes them hurt more. In fact, when I try new stuff (like using tiny DPNs) I have to consciously try to relax my hands as I'm working and take frequent breaks.
I don't know about anyone else but purling long rows hurts my hand. I don't think I hold the needles much differently but I feel the difference in my wrist afterwards. That's one of the reasons I like knitting in the round so much. I can do ribbing and lace work but only for short periods.
I've tried the little gloves that are available but didn't notice much difference. I read that yoga helps and agree. When I was doing yoga I don't remember any wrist pain. It seemed to strengthen up my hands and wrists. I've been lazy and haven't exercised in a couple of months. It's starting to look like yoga is not really an option but necessary to keep me functioning.
So I'm on a forced break for now. Sad. (And irritable).