Well, after consulting the medical book. I can safely say that I give up as i'm not really sure what to look for. But after reading it i don't think you've torn a cartiallige (sp?) or ligament as they apparantly, are inside the knee joint, rather than on the outside. Though it's quite likely that you've torn, or moved, or bruised the kneecap tendon which is right where you say the pain is.
For more information on knees see
www.kneeguru.co.uk or do a google image search for 'knee' for lots of interesting pictures of knees.
-jaffa-