knee injury

Is the pain during running, after, or both?  If during the run, is it from the outset, or does it happen after you've been out for 30 minutes?  Is it located below the kneecap, underneath, to the outside edge, etc.?

I'm by no means an expert on the subject, but one common issue is IT Band.  Another is patellar tendonitis, also known as Jumpers knee.  And there are many others.  Search the Injury forum for knee pain and knee posts.  Lots of websites with info on knee pain from running -- Google is your friend.

I had the patellar tendonitis issue, and people recommend yoga and other strengthening exercises for that as a long-term fix.  I have just been using something similar to the cho-pat straps underneath the knee cap, and those work well for me.

I began experiencing it after my first couple weeks of running, and it got progressively worse to the point that I was in regular pain after, and even during every run and having to do the RICE treatment (rest/ibuprofen/cold/elevation) all the time.  I rested from running for a couple weeks and started wearing the knee straps when I returned to it.  Since then, as long as I wear the straps, no significant problems.  I've done a couple short runs without, but I'm pretty good about wearing them.  I also don't run mega miles like some people, maybe 2-3 runs a week, usually 30-45 minutes a run, six miles max occasionally.  I suspect that people who run with minimal injury issues long-term are typically very thin.

I use the Jumper's Knee strap, but the Cho Pat one may be more running specific: 

http://www.muellersportsmed.com/kneeproducts.htm

Good luck with it. 

 Swim, bike, run (for a while, anyway, while you're getting your knee sorted).