Oh no, not the knees again

I've taken about a 3 week hiatus from running. Unfortunately after the Nielson Challenge, I started pushing myself to run faster during my training runs. As a result, my left knee started hurting again (a recurring injury that I've had since highschool) and I backed off to only running once a week for a couple of weeks. Even then, my knee was still hurting, so I stopped running completely to see if that would help. I haven't felt any twinges in a couple of weeks, so it may be time to start slow jogs again. Back to building that aerobic base...