Saw the third ortho today. He confirmed the first ortho's recommendation that, in the absence of symptoms, like pain or locking, the best course of action was no surgery. He said there's no cure for what I have, so surgery can only treat symptoms, not causes. He also said that the initial enthusiasm for platelet injections (one of three treatment possibilities suggested by the second doc) is wearing off, and he wouldn't recommend it. There is another kind of injection, called synvisc, but once again, he didn't recommend it. So basically, avoid running, and do everything else until it hurts, then go back to him. If I'm lucky, and can manage this thing well, he may retire before I need to see him again.
Still, it is tempting to see what small amounts of regular, easy running would do. I could become a one-mile specialist, or just do occasional hill work.
Anyway, thanks for all the support, info, and encouragement. The visit turned out to be a bit anti-climatic. It's a pity there were such long wait times in between appointments.
Meanwhile, cycling and lifting are going well. Rowing still sucks, but I'm doing it once in a while.