Squat Mobility Series: Hips
So, coach is constantly telling you "knees out". You do what you're told, or at least try to.
But you might ask yourself:
“Why?”
“I thought I was”
“But I can still lift the weight doing what I do”
“I know I know”.
When does it happen? Squatting, wallballs, dipping movements such as push-press and jerk, box jumps, jumping, running, catching a clean and snatch, and even sometimes deadlifts! With squats, it can easily occur coming up from a squat as well as down. Here is what it looks like:

Why does it happen?
Having Weak Hips: These weak/inactive muscles include your gluteal muscles (your bum muscles!), and hip external rotators (outer hip). This weakness in the glutes and outer thigh is usually accompanied by overactive/tighter inner thighs (adductors). If you can visual - the hip muscles are weak calling the knees to “fall” inwards, and the inner thigh muscles are tight - “pulling” the knees inwards. A dangerous combination.
How to fix it? Strengthen hips and glutes, and stretch out inner thighs to allow.
Strengthen hips/glutes:

Clam Shells
Glutes Bridges - For extra goodness, leave the band on and as you squeeze your glutes up as tight as you can, push the knees out against the resistance.

Squatting with a Dyna-band - Same idea as glute bridges with a band: as you move upwards and downwards in your squat, resist against the bands to activate your outer hips/glutes more through the movements
During squats, take your time and “feel” the movements. Add weight as you gain better control of your hip strength, and if a weight causes your knee to uncontrollable buckle, drop the weight down to a challenging yet doable load. Never Ego lift.
Stretch Inner thighs (Hip flexors and adductors)
1. Lateral Lunge/ Cossack Stretch

3. Quad Stretch - Place a ab-mat underneath the knee if you find this too uncomfortable.

4. Frog Stretch

So there we have it folks, if this problem seems like a bit of you, try these exercises out - they are some of my personal favourites to do and recommend to others.