Knees bowing in on squats
I may have solved this problem, by playing around with my body.
For me, it's because of a lack of hip abductor flexibility. I think in my gluteus medius, but I'm not sure. The telling sign is I can't put my leg in a "figure 4" while sitting at all (for my right leg). It puts stress on my ankle and knee instead.
So ordinarily, glute stretches would do the trick. Except they stretch my ankle and knee out more than my glutes.
A weird modification, where I kneel down on the OK leg "prayer style," and make a figure 4/butterfly with the offending leg. With the opposite hand, I grab my foot so as to keep it perfectly parallel to the ground, so that I don't stress my ankle/knee while stretching.
Then, I lean over as you would in a butterfly or hamstring stretch: back neutral or arched, chest up. Kapowy, major stretchin' of the offendin' junk.
I guess the moral of the story is, if you're knees are bowing in, look for:
ankle mobility (I checked this first, it was OK)
hip mobility (ability to externally rotate the hip so it matches your "toes out" angle, so that your knee can line up with your feet).
I think the hip is the more likely problem here.
If you can sit Indian-style, or in a lotus, then you're probably cool.
Oh and for me, it was only my right leg. This caused the sensation of "leaning over" onto my left leg for driving out of the hole in the squat. It was like I was pushing more with my left leg all of a sudden. I believe it's because of right leg bowiness.
Stretching + glute/abductor activation + "shoving the knees out" = success for bowing, I believe.
If this is obvious information, then um, I'll delete this thread.