Quote Originally Posted by Fozz View Post
A good way to prevent or at least limit the lower body movement is to concentrate on bracing the back knee (in your case the left knee). You should try to feel resistance to the inside of that back knee all the way to the top of your backswing. Like the others said, a little wider stance and a more knee flex (slightly) will help achieve that.
A good drill is to place a stable object under your back foot and take an easy swing. Something like a one inch board will do the trick. It will keep your foot from rolling over and encourage keeping the back leg from moving laterally.