Add Kick To Your Drives: Maintaining the flex in your right knee will help you stay in your posture and deliver more speed at impact.
Tension is a main culprit in many of the faults that ruin golf swings. And it's not just arm tension. I like my students to maintain the feeling of a soft right leg on the downswing. This requires them to flex the right knee slightly at address and increase that flex as the club swings down. The knee should be pointing at the target line in front of the ball as the club approaches impact.
Many amateurs lock the right leg as they swing down, causing them to hang back and hit weakly off the right foot. Others move the right knee laterally toward the left knee; this is a result of the hips sliding instead of rotating. Either way, many amateurs don't shift their weight to the left side through impact. Sometimes the leg muscles are so tight they restrict movement. Remember: Relaxation assists fluidity.
Focus on flexing your right knee at address and during the downswing. That helps you maintain the correct posture and promotes a more powerful swing through the ball.