Hitting from the rough resulted in decreased total vertical loads across the knee. However, hitting from the rough resulted in higher focused loads across the lateral compartment of the back knee at impact. This was thought to be due to the greater resistance of the club head going through the tall grass prior to hitting the ball buried in such. It is also possible this player may have stayed back on his right leg at impact.
Modification of the Forces: Various methods were explored to reduce the forces across the knee joint during the golf swing. The most effective way in our study to reduce the loads across the knee joint was the use of a proprietary Golf Specific Insole. The 2.5 degree wedged insole had less dampening effects on the total loads than the thicker 5 degree wedged insole. The 5 degree wedged insole was effective in reducing the total forces across the knee and specifically the lateral compartment loads. The insertion of the 5 Degree Wedged Cushioned Insole reduced the total forces off fairway on the right or back knee by 15-20% and average of 25% when hitting out of the rough. This was probably due to the thicker depth cushioning effect of the 5 Degree Wedged Cushioned Insole.
There was minimal difference in unloading the back knee’s lateral compartment with an “unloader” brace at 3 degree setting. However, there was a 56% decrease of the load on the lateral compartment at impact when the brace and the Golf Specific insole were used in combination.
Testing on the right handed subject with the left or lead E-Knee showed differences in loads only at impact comparing the foot perpendicular and turned out 45 degrees. The turned out position reduced the axial load through the knee at impact. However, it increased by 5% the load on the lateral compartment at impact on the left or front lower extremity.
USGA Ruling: As of March 31, 2009, the use of these 2.5 or 5.0 degree sloped cushion wedged insoles are included on the List of Equipment Permitted Conditionally for Medical Reasons. They are “Permissible when the local committee authorizes its use under the List of Equipment Permitted Conditionally for Medical Reasons and/or Exception 1 to Rule 14-3.”
Answering the Hypothetical: The question so often asked is how much is the load on the left knee of a right handed golfer at a swing speed of a professional golfer, i.e. 135 mph? It is probably very high, but there is not a direct means of calculation. Therefore, the golfers’ with lower swing speeds were asked to swing at varying speeds at 10 mph intervals. Two of the subjects, good golfers for their age were able to so.
The chart below shows that the progression of swing speeds has a linear relationship to the axial (total) load or peak force across the knee joint. This evidence supports the concept that the faster the swing speed the greater the peak force across the lead or left knee at impact with the ball with a long shafted club (driver).
Therefore, the peak forces across the knee are likely very high at a swing speed of 135 mph, typical of the best professional golfers.
