I developed the same problem in both of my knees and fought with it for years (late teens to mid-20's). I was a ballet dancer for a number of years which overdeveloped my outer quads. Mine were so bad that I could barely walk through the grocery store by the end. I had surgery (lateral release) done on both and can do pretty much anything now. Running is the only thing that hurts (sometimes).
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Elizabee (age 5) at the doctor's office: "I can smell sickness in here...I smell the germs"