The operation went without a hitch. They were precisely correct about what the problem was - I had a minor meniscus tear, like "a hang nail." They clipped it and sewed me back up. After a 9:30 operation I was back on the street with a pair of crutches by noon.
I am not happy about not being able to shower until Sunday, I have to keep my leg wrapped until then. And though I have been trying not to tax myself, I misjudged today and had a long hobble from the bus stop to my home. At least, as Ali points out, I am getting an upper body workout.