Instead, 2 days ago one friend happened to be in the gym and he told me I had my bar tilted to one side while squatting, pretty badly. Now obviously I couldn't feel that on my back but I kind of expected it... I'm not sure though if it's because of my right knee pain or because of my left hip pain. Haven't asked him to where it was tilted (left or right).
It could also be because I load the left leg (MUCH stronger quad there) more than the right leg (weaker quad).
I think that's one (if not THE) reason why squat-built athletes (think Squat DR, Kingfish, acole) plant their both legs at the same time - because they don't have a CLEAR stronger leg on which to plant and rotate into their jump.