I have a contact in the health-fitness industry point me in the direction of this condition after I explained I was having an on/off pain under my kneecap.
Need a map? http://www.innerbody.com/image/skel12.html
http://orthopedics.about.com/cs/patelladisorders/a/kneecapdisloc.htm (not this bad, thank goodness)
Usual disclaimer about not following self-diagnosis and getting a 2nd opinion from a medical professional applies.