Golf tip: For power and accuracy keep left knee firm but flexed

“Hit against a firm left side” is a classic piece of swing advice that many golfers misinterpret. They think it means that the left knee should be stiff and straight during the downswing- a mistake that forces tension into the leg, halts hip rotation, prevents proper weight shift to the left side, and destroys clubhead speed. At impact, either the left arm collapses (Fore left!) or the hands don’t release (Fore right!). Not pretty.

Ernie Els had to miss the 2005 President’s Cup while recovering from surgery after tearing ligaments in his left knee while tubing in the Mediterranean on a family holiday. For two years, Els was unable to shift his weight properly into his left side because he would stiffen his left knee at impact.

But after many months of rehab and a few swing tweaks, one which included keeping the left knee firm but flexed, he was back at the 2007 President’s Cup and defeating the Lucas Glover of the U.S.

In fact, if you watched the President’s Cup matches this year, you would have seen that all the good ball strikers had a firm, but flexed knee through impact, not stiff and straight. When you keep your left knee flexed, you’ll be able to rotate your hips fully and freely during the downswing.

This rotation is crucial, not only for building clubhead speed with the rotation of your body, but also for keeping the clubface square to hit accurate shots. By properly clearing the hips, you give your arms room to swing the club down and through the line-in other words, to hit the ball straight. The left leg straightens only well after impact, when nearly the full weight of the body shifts onto the left side as the swing progresses from follow-through to finish.

Again, when it comes to the left knee, think “flexed and firm,” not “stiff and straight.”