Im gonna throw my 2cents in on this, im guessing yo squat heavy and only bout 1/4 deep, as stated earlier your psoas looks overly developed causing some rotation but more importantly your VMO looks uder developed and from the angle of your leg it looks as though you posterior is under developed also these can cause that sinkage and rotation your experiencing
Squat deep activate your VMO and posterior, will help greatly
Hope that helps in some way