I honestly don't know, but I don't like this happening again 10 minutes into my run. I did try pushing past it, but no.
So today it's a case of searching the net to see what I can figure out. I know it's not fatigue, my mileage goal make look insane, but that's just recording the walking I normally do as well as the running for a Nike+ challenge. So that leaves nutrition and stretching to work on.
Starting today: I will lay out my vitamins for the rest of the week and make sure I take each one. I think I'll start by moving my PT to the front of my run instead of end. Perhaps that will help loosen things up enough.
Tomorrow instead of running in the AM and walking the Marsh Post course, I will walk in the AM and PM and see how that feels. I'll take Friday off, walk Saturday and my "long" run Sunday will maybe be 3 or 4 miles. If I can't make it through Sunday's run, I'll call my orthopedist on Monday.
Sounds like a plan.