Squat Form-Struggling with knees caving in

[pk315]

Video-185 x 5

Imgur: The magic of the Internet

My knees cave in when I squat, how can I diagnose and fix this problem? I’ve been doing hip abduction exercises for the past month that don’t seem to be helping, and I’ve tried to “screw” my feet into the floor. I was looking at an old thread on here where Mark said something like “knees cave because you let them cave”. I wasn’t exactly sure what he meant, but it sounds like he is saying it is caused by improper technique, not muscle imbalance or weakness. How can I train myself to do it properly?

I should also add that this doesn’t happen on lighter weights. I was messing around with 135 and did 10 reps with no caving. Even at the end of the set when I was approaching failure they didn’t cave.
Thanks!

[Pete Troupos]

Please film from the angle that's asked for in the sticky at the top of the forum.