Should I wear a knee brace?

I apologize in advance for a total lack of medical terms:

Ok, just getting back into things after the birth of my third child and some injury issues. One of my problems involved knee pain. However, it didn't hurt at all when I'd run, but the next day would be really painful when I'd be going up stairs, getting out of the car or generally putting weight on it in a flexed position. I went to a sports doc, and after x-raying my knees and working with me a while, he said that my problem is that my kneecap doesn't track straight up and down in the proper groove, but rather follows somewhat of a J-shaped pattern. He gave me some exercises to do - leg lifts while lying on my side, leg extensions - to strengthen certain leg muscles and hopefully keep the kneecap in proper place.

While swimming this morning I was chatting with a woman who has done a few Ironmans, and she suggested that in addition to these exercises, that she thought it would be a good idea to also wear a brace while running to try to help keep the kneecap from slipping out of the groove.

First, does anyone know the medical term for my symptoms, just so I could try to do some more research? Second, for anyone who has experience with this sort of thing, do you recommend the brace, and if so, what kind?

-Matt