I’ve got quite the same problem as all of you here. While squatting my knees just keep pushing out by themselves and I constantly feel pressure in hip extensors, butt wink is never good, etc. So, I started doing a lot of mobility exercises for hips, hams and glutes, also strengthen my core with bunch of various planks. Not much improvement has been seen, so i went to my physio. He performed a few tests on me, as internal and external hip rotation tests, hip adduction, etc. He doubted on thing called “femoroacetabular impingement”. I went to doctor to check this our, took MR and it was positive. So, my problem was hip degeneration, and as doctor said, about 10% of young athletes have got the same problem without even knowing. I’ll be going on both hip arthroscopy very soon, doctor expects it all to be fixed and corrected. I don’t say it’s the same case as written up here in those posts, but I was just so frustrated about not being able to find the reason of my bad squatt, so i went to doctor. I hope this is not the case you have, but it will be worth checking out with doctor.