First 17 were at 7:30/mile. Then things came unstuck. The right knee started first (not surprising). It got a bit better when I slowed down. Then at mile 20 I picked it back up, only to encounter some really serious knee pain within 1/2 mile. I considered stopping, but decided 'what the heck?' and kept going, albeit much slowed, around 8:00/mile. I pushed it the last mile, probably doing around 7:40.
Flat, easy. The only real problem was the idiots who started in the 6:00/mile group but ran 9:00/mile. Once I cleared them, it was easy sailing.