The mobility of the knee joint enables a significant amount of rotation and force throughout the golf swing. The position of the knees changes with each segment of the swing and plays a key role in linking the legs with the upper body. PGA teaching professional Mitchell Spearman recommends checking the position of your knees in a mirror to gain instant feedback and make corrections for each swing segment.
Flex your knees slightly when you address the ball, as if you were sitting down in an imaginary chair. Ben Hogan believed that the legs should bend, from the thighs down, while the torso remains fairly erect. The knees provide stability, and Hogan asserted that when the knees are properly flexed, the golfer can rotate the hips and shoulders with ease.
The knees should be flexed during the initial part of the takeaway. Once the club reaches parallel to the ground and you begin your shoulder turn, the left knee remains flexed but the right knee straightens. In his earlier years, Tiger Woods was notorious for snapping his right leg straight because he believed it increased his rotation and gave him a sudden burst of power.
Top of Swing
At the top of the swing, the right leg should be completely straight and the left knee should be slightly flexed and pointed toward the right leg. Hogan believed that turning the left leg in and slightly rolling the left foot inward helped shift his weight from left to right, thus adding more power.
The downswing is primarily initiated by the hips, according to Hogan. As you swing toward the ball, the hips unwind, which straightens the left leg completely. The right knee bends to allow the right side of the body to completely rotate through the ball. Hogan believed that turning the right knee toward the ball added significant velocity to his swing.
At the finish, the hips and shoulders have completely unwound, leaving the golfer facing the target. The left knee is still completely straight or just slightly flexed to reduce the impact of the powerful torque on the knee joint. The right knee is flexed and pointed down to the ground, parallel with the target line.