I used to have a bad problem with wrist pain at work. (I was an executive assistant, so I was on the computer constantly.)
They sent me to an ergonomics specialist, who advised me to change the height of my desk, change the way I was sitting, and put my computer keyboard on a tray that flipped out from under the desk.
The pain went away completely.
I’m sure there are things you could do differently when knitting and spinning that will help with the pain.
Do you have a video camera, or could you borrow one? Try videotaping yourself spinning and knitting. Then, think about what you could do to keep your back, arms and hands at a more comfortable angle. Maybe you’ll need a different chair or a thicker cushion. Maybe you should adjust the angle you are holding your arms or hands. Maybe you are unconsciously putting weight on your arms or hands.