I am pleased to report that time and [nearly] a week of not knitting has largely cleared up my thumb joint issue.
Can I get a big HURRAH!
Although I had declared myself to be a non-knitter for a week, I held out for only four days. Thank FSM, that seemed to be enough to heal most of the injury. I have been happily knitting ever since. There is still a little residual pain, but as long as I am not knitting something stupid, like the mittens below, it continues to improve.
During the hiatus I thought about what might have caused this pain and suffering. It did not take long to identify the culprit(s):
In particular, the mittens on the right, those nasty ones that didn’t match each other.
These are three of the items I knit for the local warm clothing drive in December. The yarn was O-Wool Balance Bulky, a 50/50 wool/cotton blend, and we all know what that implies: less elasticity than a 100% wool yarn. This was not a problem in the hat and scarf, which I knit on US#10-1/2 and US#11 needles, respectively. But I wanted the mittens to be dense and warm, so I went with a smaller needle — US#9, maybe? I didn’t Ravel the mittens because I was so ashamed of them; thus, no record of the needle size.
Anyway, knitting a bulky, non-elastic yarn on US#9s was apparently just too damn much for my dainty paws, and my thumb joint paid the price.
Lesson learned (I hope).