I don't know about the heel hooking issue but I am guilty of using the drop knee alot. I've found hip flexibility really key in relieving stress on the knee. Do these while watching telly:
Lie on back, straight legs, pull one knee to chest with the knee bent. Feel the stretch across your bum.
Lie on back, bend knee at 90 degrees, raise knee to ceiling and arc towards the floor crossing your body. Keep your shoulders on the floor and feel the stretch on the outside of the hip.
Lie on back, bend knee at 90 degrees, foot on floor a shin distance from the other knee and drop the knee towards the other knee just like an egyptian. Feel the stretch on the outside of the hip. Avoid tweaking the knee.