Proper understanding of how rotation works in your hip sockets can really transform your swing. So many people that come in for a demo at Alta View struggle with an inside takeaway or a loss of posture through impact. It is clear that improper rotation between your legs and your pelvis in the hip sockets can readily contribute to both of these swing faults.
Dr. Tyler Standifird from Utah Valley University shows how the sequence of rotations in the hips sockets works in this video.
As you look at your swing on video there are a couple of key points that you can look for to help you see if you are doing the proper rotations:
Your kneecaps should point forward during the backswing and during the transition. Excessive rotation of the legs relative to the target line means you aren't rotating in the hip sockets. The knees should not rotate in the same direction as the trunk rotation in the backswing. For the right handed golfer the pelvis will rotate about 45 degrees to the right and the kneecaps should still face forward so the legs are now rotated left relative to the pelvis while the trunk is rotated right of the pelvis. The legs do not spin in lockstep with the pelvis!
You should see a crease in the fabric of your trail side groin in the backswing - indicating internal rotation of the trail leg in the trail hip.
You should see a crease in the fabric of the lead side groin as you finish the swing - indicating internal rotation of the lead leg in the lead hip.
Here you can easily see how Adam Scott has his kneecaps still pointing forward and the legs are rotated left relative to the pelvis while the trunk is rotated right of the pelvis. The right leg is internally rotated in the right hip socket which generates the crease in fabric in the right groin. The left leg is rotated externally in the left hip socket. This will reverse through the the transition, impact, and the finish position.
The legs apply torque to the pelvis through the hip sockets. This torque coming to the hip from the leg from your interaction on the ground counterbalances the torque applied to the pelvis from the trunk rotations to the right and left. When you learn to have these torques in balance you have a very stable spine during your swing which is described as "maintaining posture" and that is huge in creating consistent ball striking.
So if you see your pelvis extend early in the swing with your pelvis moving towards the target line at impact you a likely factor is you don't have enough torque in the hips applied in the proper direction and time via the internal and external rotation of the legs.
We have great instructors at Alta View that can help you will drills and feedback to help you learn how to properly use rotation in the hips. Just send us a message as we will get you setup with a terrific lesson!