spreading knee pain

Hi. I'm an 18 year old male who was diagnosed with Anterior Knee Pain Syndrome last September on my left knee. I was given a brace to provide support as my knee would give way sometimes. Today i woke up and I had my usual pain that lasted for about 5 minutes. Up until about noon, i was ok. But then my Quads started hurting and feeling weak. Up until now they still are. It's been about 6 hours already. I'm not sure if maybe the Quads have weakened or not, as I'm not really active right now, being in school. I was running yesterday, a light jog. Could it be that it is the quads that have become weak, or could it be something underlying? Thank you.