Sorry to hear about your knee pain, Erin - I hope it settles down you soon!
I am dealing with lots of knee pain in my left knee at the moment right now also. The pain is awful and because I have a chronic pain condition on top of it, it has thrown everything out of whack.
I'm not sure what is causing my knee pain but my PTs have been using a splint on my leg in PT to try and correct the Dystonia in my foot and leg and during my last PT session over a month ago, they got me walking in it and my leg kept shooting out and twisting and I recall complaining of bad knee pain so i'm thinking that did some damage but wont know for definite until I see my PT's next Wednesday.
My mum called my doctor and he said to go and see my GP to get some anti-inflammitaries and to rule out any other possibilities, especially seeing as though it's not the usual pain I get.
I posted about my knee pain in the RSD forum and someone replied and mentioned a condition called 'Patello-femoral Syndrome' as I had a lot of the symptoms. I have done some reading up on it and I seem to have all of the symptoms but obviously can't get it diagnosed until I see an Orthopaedic Dr.
The symptoms you described sound exactly like what I am having. My knee is extremely painful, especially when I bend it or move it and the knee cap also swells up and goes red and tingles. I am also noticing that I am losing my balance often and it feels as though my knee is really unstable.
I hope you can figure out what is causing your knee pain soon and can get it treated quickly!
Keep us posted on what you find out, if anything!