Well ive had this problem from the dawn of my weightlifting career, Whenever i get to my top set on squats i have a lazy glute (which i beleive was caused from a high school football injury) which makes my knee cave in. This makes my form look like shit, and obviously its not safe going around squatting like that. There’s and old video in my profile of this happening. I’ve tried lots of stuff to help it, like a crap load of single leg work, foam rolling, mobility drills, blah blah…all have helped me, but it never seems to be quite enough. Sometimes it seems to be worse then others. For a while i felt things were going pretty good during the summer, but then i took deload week and when i came back to squatting the next week the problem was MUCH worse. Very frustrating.
Anyways i was influenced by this article Strength Training, Bodybuilding & Online Supplement Store - T NATION
which reccomends switching exclusively to a single leg squat movement. I think doing this definately solves the knee cave problem. But im worried it might not be great for hypertrophy of the quads. I will still probably use a leg press as my 2nd quad excersize (no problems with that movment, except gotta be carefull with the back) But im worried the single leg squats would only add mass to my ass as ive done rear elevated squats (only with dumbells) before and felt the insanity in the glutes, less in the quads.
I have mixed feelings about unilateral leg training. I used to avoid squatting all together because of lack of skill, some back problems, and just preference. I would do deadlifts, single leg squats, and stepups. This worked pretty well, but progress halted pretty quickly. Then I started doing front squats a lot, and became very comfortable with them. Now im finally working in back squats and they are so easy compared to front squats.
I try to work in split squats with a barbell, but it is really awkward and I feel i’ll get a limited effect since I cant go too heavy. Im sure eventually like all other things i’ll come around to them and make great progress from them.
My problems with squatting were a bit different than yours, but some of the things that helped me are:
Hopefully this helps you. Just work around the problem while you are trying to adress it. Cut back on the heaviest sets of squats until it dissapears. Also, I didn’t do these, but maybe do some squats with a mini-band around your knees to teach you to prevent legs from caving in.