my knee tendon ( out side of the knee, around where the outer quad attaches) pops/rubs when bent past parralell, ive seen a doc about it and he wont do nowt till its totaly gone, so ive avoided anything full range, my quad workout is extensions supersetted with ham presses on a leg press( feet high on the platform, low range of motion)... i could squat over 4 plates comfortably before i started gettn bother with it, still hanging on to some size playin around with my daft routine