Lie on your side with the hips and knees bent and a medicine ball between the knees.
 
Squeeze the ball with the legs continuously as you internally rotate the upper leg to lift the foot, then return to the start under control.
 
The bend of the knees and hips can be changed to mimic the position in a squat or jerk dip in which valgus motion or weakness is most pronounced.
 
Resistance can be increased by adding a mini band around the ankles.
 
Notes
Pay attention to which side feels weaker and less mobile and do more reps or sets on that side.
 
Purpose
The sidelying hip internal rotation + iso adduction strengthens the hip internal rotators and adductors to improve hip stability and mobility.
 
Programming
Do 2-3 sets of 10-20 reps.