I'll make this short since I'm pretty sure you don't care about my knee caps. =)
About a year ago I started having severe pain in my left knee when I ran or went up stairs. After seeing a chiropractor, podiatrist, and orthopedist I ended up with a steroid shot. While it took care of the problem, it wasn't a good solution. It only put a band aide on the problem. Fast forward several months and my right knee starts having issues. I decided to go a different route when I ran 9 miles a few weeks back and experienced the worst pain of my life.
I am now seeing a physical therapist two days a week and can tell a huge difference already. Apparently the main issue (I have quite a few, sadly) is that my knee cap is "off track" and is causing pain when it grinds against my bones. So I'm doing about 2 hrs of exercises every day that are getting it back into position. My knee is still painful whenever I bend it, but I ran 31 miles this week with considerably less pain than I experienced previously. Twelve of those miles were this morning. I'm now ready for my race.
It was a good run, despite the pain and I'm really looking forward to running my first half marathon in April.