I tried to find this discussion already, but it seems y'all are talking about regular front knee or side knee pain.
I sometimes have horrible pain behind my knee, on the backside of my leg. It showed up on one of my 5k's and then I was fine for a 10k and 12k. It showed back up a month later on a 1/2 marathon and I could barely bend my leg to move forward. My quads don't hurt.
Any ideas?? I've been off for a few months and started running low (1-2 miles) and it's fine so far. What is it?