RockSolid

I have been working out for a few years now and I have always had trouble maintaining my leg stability when I squat or deadlift. I like those excercises but when I put the weight high enough that it challenges my muscles my joints dont hold like my muscles. My brother is an excercise science major and he said I have a protruding "navicular" bone in my foot which is a sign of genu recurvatum and my knees do bend backward to an extent much more than normal without me feeling any sort of discomfort whatsoever...Anyway to keep it short does anybody know about this and what could I do? My legs are still pretty strong; for example I do SLDL with 140+, I do walking lunges with 90-100lbs but doing things that require stability in my knees is very difficult and annoying because I have the strength to do it but it doesnt get done...