Now we have your knees and legs in a strong position we can change the way your hips work in the swing. The hips should turn (right picture), not slide (left picture), 45 degrees is roughly what we are looking for. There has been proven to be a direct link between the amount your hips turn and the distance you hit the ball.
So turning your hips is a power move!
Your knees are designed to flex and extend (like a kicking motion) but what they are not designed to do is twist. So why to we try and twist our knees in a golf swing? What I look for is the left knee to flex forward and your right leg to straighten. This action will force your hips to turn instead of slide creating a strong lower body position. What I am not saying is for you to allow your right leg to lock out! I am asking for it to straighten in comparison to the flexed position it started in. As I mentioned earlier, the amount your legs will need to flex and straighten will entirely depend on your body.
This will ensure your legs will create a powerful position and turn at the top of the swing allow you to achieve your maximum potential for power.
Here’s a great drill to exaggerate this! Take your set up and before you start your swing, flex your leading leg forward and straighten your back leg. By starting in this position it will give you the feelings of an exaggerated correct movement. Integrate this drill with some normal shots and watch the results improve! Just look a the position Ben Hogan used to get to at the top of his swing, arguably the best ball striker of all time. His left leg is clearly flexed forwards with his right straightened.
So enjoy the drill and enjoy your practice!