My age and condition (40+, diabetic) plus my hobby (knitting) are all risk factors. They don't list knitting per se, but any activity where you grip somethng tightly for a long period (like, say, a kniting needle) will cause/aggravate it.
It's treatable with rest, ice and nsaids, but there is also surgery - surgery that actually *works* and isn't long-term disabling.
Meanwhile, my best bet is to not "trigger" it - no knitting, of course, but also, I've been, you know. Testing it. Bending the thumb to see if it catches. Which hurts and is weird, but it's a human thing to do. Except not a good idea.
I'm also wondering about changing our trackball to a regular mouse.
Stopped wondering and did it - the new computer came with a mouse, so I just installed it.