It got so bad this evening that I could bear no weight at all, so I called the triage nurse and was sent to the emergency room. My excellent next-door neighbor helped me get out of the house, down the porch steps and into the cab.
The doctor there doesn't know what the problem is, but they eliminated a bunch of stuff. He says it is not neuropathy, the pattern of pain isn't right for that. If it's an infection, it isn't far enough along to show in the blood test. and they took x-rays, and the prelim reading says no busted bones. So he thinks I've torn a ligament, probably, and sent me back home with an orthopedic bootie and a prescription for really good pain pills. (and gave me two before I left the ER and two more to hold me until I can get the prescription filled in the morning) They don't get rid of all the pain, but getting from 8/10 to about 4/10 means I can grit my teeth and hobble to the bathroom without screaming, which is a very good thing indeed.