Thanks for reaching out Michael and thanks for your feedback Les! If you are having pain in the left knee beyond any usual training discomfort we would encourage you to consult a medical professional as their may be more going on in your knee than what meets the eye. As it relates to the training, it’s very possible you are missing some key elements because these movements are designed to take undue stress off the joints. It’s important to understand the function of the knee as well. The knee is a modified hinge joint, which permits flexion and extension as well as slight internal and external rotation and is not designed to functionally move outside of those parameters. That being said when we perform our downswing movements (surf the knees, snap to level etc) we want to make sure the left knee (RH player) is still flexed or slightly bent and is moving perpendicular to the angle of the front foot at setup but not moving independently. Because the front foot is slightly flared out, the left knee, left shin, left thigh should all move on the angle of that foot. To Les’s point above, make sure your left knee is not pushing forward as you snap to level or extending backward straightening the front leg destroying all strength and leverage. Over time the body should be in pain if we are snapping the knees incorrectly in the downswing. We would encourage you to perform the stretching routines throughout the week to help open up the body and to go back to chapter 1 to make sure that you are understanding how the knees function correctly in the golf swing. If you are interested in more personalized 1 on 1 training you can receive personal analysis of your movements through the additional training tab on our site. We hope this helps and thanks again for reaching out!