Folding your right knee (for a right-handed player) as you address the ball, then maintaining your knee in a flexed position for most of your swing, is a key element in sound golf swing technique, according to PGA professional Carl Rabito. When students come to him with common complaints, such as slicing, frequent mishits or general inconsistency, Rabito says one of the first two things he examines is the player’s knee action.
Flex both knees in the address position. In his book "The Complete Golf Manual," Steve Newell says players should maintain “a comfortable amount of flex” in their knees when they set up to the ball. Flexible knees help golfers perform a proper body turn during the swing.
Maintain the bend in your right knee during the backswing and through much of the downswing, Newell advises. Maintaining the flex in the right knee during the backswing, he says, creates resistance in your legs and hips, which prevents the backswing from becoming “too long and uncontrolled.” Keeping the right knee flexed until at least the midpoint in the downswing helps keep your right heel on the ground for a longer time, which in turn gives you a wider downswing arc. This wider arc is particularly important when you’re swinging with a sweeping motion -- as opposed to hitting down on the ball -- such as when you’re teeing off or hitting a fairway wood.
Gain more power on your shots, particularly off the tee, by folding your knee during the downswing, says golf instructor Jim McLean. McLean advocates flexing your right knee “slightly” at address, then increasing the flex as you begin the downswing. The right knee “should be pointing at the target line in front of the ball” just before the club reaches the impact zone, McLean adds.