During a squat, it's important that your knees stay in line with your toes during the entire movement. You want to be cautious of your knees buckling inwards as this can potentially cause unnecessary stress on your knee joint, and also inhibits your hip movement and activation of your gluteal muscles. 

What can you do if you experience this problem?

Use a resistance band

Putting a resistance loop band around your thigh (just above your knee joint) provides a cue to push your knees out as the band is trying to pull them in. This allows more movement through your hips as well as greater stability through your hip and knee joints. Pushing your knees out against the resistance band will also help to increase the activation of your glutes as they are at a mechanical advantage in this position.

You can use this technique regardless of the type of squats you’re doing – including barbell (front and back), goblet (with a kettlebell) or even just body weight!