Bad news: my knee hurts.
I have been devoted to the 10% rule, so I don't think it's overuse. In fact, it seems pretty clear that running on the uneven and slippery terrain we have outside was the cause. Somehow, I must have slid too much and put too much strain on my knee.
Regardless, I'm taking an unplanned day off today. I have an 8K to run on Saturday, and we'll see how it goes.
Think positive for me!