The month before my half-marathon I had ITBS (Illiotibial Band Syndrome), sometimes called "Runner's Knee". My doctor gave me some strengthening exercises and stretches to help strengthen my hips. It went away over time, and I have yet to have an issue.
I had gotten a really handy IT Band Strap that allowed me to run my half relatively pain-free.
During my recovery, I did cycling and swimming instead of running. When I was able to gingerly get back on my feet, I did my running on natural trails as it was easier than pavement.
Here's some good info on ITBS for anyone that suffers from it:
http://strengthrunning.com/2011/02/the-itb-rehab-routine-video-demonstration/