There is a joint at the base of your thumb called the CMC joint. Every time you pinch a needle and stitch, that joint takes the load. Do it for an hour, a day, fifty years, and the joint starts to shift and slide under the strain.

That sliding is what you feel. It starts as a deep ache right at the base of the thumb. For a lot of knitters it radiates up toward the elbow. Some describe the thumb "popping out of joint." And it always seems to show up at the worst moment, right when you've finally sat down with your yarn.

Left alone, it steals the thing you love. Knitter after knitter says the same thing in our comments: they were forced to give up knitting. Not because they wanted to. Because the ache made them put the needles down.

Here is the part almost nobody tells you.

Stretches don't stop the joint sliding. Pills don't stop it sliding. A cortisone shot quiets the inflammation for a few months, then it comes back, and the next shot buys less than the last.

Until the joint stops shifting while you knit, you are only quieting the ache, not the cause of it.