Scientific Study Golfer’s Knee Stresses

Golf is hard on the knees, especially ones that have had injury or arthritis. Read on to see a scientific based solution that will allow you to continue to play a game you love and it seems your knees hate.

Background Facts:

  • It is known that excess loads across the knee result in cartilage injury.
  • It is also known that cartilage does not heal like other tissues as it has no intrinsic blood supply.
  • It is known that decreasing loads across a joint will result in recovery or repair of a previously injured joint, even in degenerative arthritis. (see Medical Literature)

Therefore, finding a non-operative means of unloading the knee joint for activities of daily living is of great interest.

The knee joint has not been extensively studied in relation to the sport of golf. However, recent media reports have drawn attention to knee injury and treatment in golfers, especially prominent professional PGA tour players.

Scientific Advances: The Shiley Center for Orthopedic Research and Education (S.C.O.R.E.) at the Scripps Institute in La Jolla CA has four patients with an experimental total knee implant. It is called the electronic knee or E-knee for short.

Lanny L. Johnson, M.D.
Xrays of E-Knee in place
Testing apparatus with sensors on the knee

The ingenious idea was conceived by Clifford Cowell M.D. and Darryl D’Lima M.D. at Scripps. They have reported extensively in the medical literature on their findings primarily related to issues concerning total knee replacement designs and function. They have won many scientific awards for this contribution.

Ongoing Studies at S.C.O.R.E: Results from studies concerning unloading of the knee joint for activities of daily living have been promising. To better understand the significance of the study’s results, the following benchmarks need to be understood.

When one stands evenly on both lower extremities, half of one’s body weight goes through each knee.

During walking 2.5 X one’s body weight goes through each knee with each individual step. This increase is due to the slight shifting of the upper body side to side with each step.

We have evidence we can unload the knee joint for activities of daily living. These same principles are being explored concerning the golf swing and potential injuries.

Published reports from SCORE have included preliminary studies of the knee loading in the golf swing. Using several senior citizen subjects, octogenarians, with a golf swing speed of 65 mph they have determined on average the back knee is loaded 3.25 X body weight and simultaneously 4.5 X body weight when the club is at the bottom. Those results were surprising, but raised the question of knee joint loading during the golf swing of a professional at 135 mph. It is not possible to exactly project such a force, but certainly it is believed it would be much greater.

Recent Results of Right Handed Player’s Back Knee: Being surprised by the loads on the knee in the golf swing under those conditions, further studies were warranted. Under the direction of Joe DeBock, head golf professional at Torrey Pines Golf Course in La Jolla, CA, we performed live testing. The recent subject was a man with a slightly knocked knee joint alignment following his E-Knee replacement. This replicated the condition of arthritis on the outer side of the right or back leg of the right handed golf swing. (Results of studies on the left knee are forthcoming.)

Live testing of Knee Loads on Golf Swing

Testing showed similar high loads across the knee joint as before which was perfect for testing of various modalities to reduce the loading during the golf swing.

Tests were performed with and without spiked shoes. It was surprising that soft spikes reduced the load compared to soft soled tennis shoes. It was thought the fixation to the ground with spikes would have prevented dispersion of the loads, but the evidence was to the contrary. The explanation was not readily apparent.

Tests were performed to compare hitting off of fairway level grass with a wedge compared to hitting out of the rough.

Wedge approaching the ball buried in the rough

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.

The linear fit line has the equation y= 0.0323x + 1.0675 where "x" is the club speed. In theory, extrapolating from these patients, if Tiger Woods can hit at 120 mph, then y = 0.0323*120 + 1.0675 y =4.94 xBW.

Protection of the Knee Joint Compartments in Golfers

What position of the left or lead foot in a right handed golfer is the best for various knee conditions? It has been traditionally thought that turning the lead foot out would decease the loads on the lead knee. That is true in part.

Independent testing has shown that turning the left foot toe out 45 degrees (used in testing to make sure we got an effect) will reduce the total loads across the knee. However, that position will increase the loads on the lateral side of the knee.

The following bar graph of our results will discuss each variable in the golf swing and unloading the knee by foot position and use of these proprietary cushioned wedged insoles.

Mediolateral Force Distribution

The bar by bar analysis of the results may be helpful to understanding. The bottom bar is the control bar, meaning there were no appliances utilized, just the golf shoe with soft spikes. Incidentally, the soft spikes themselves dampen or lessen the axial load at impact. What effect that has on the following results is not known. We did not have the subjects hit balls bare footed.

Starting at the top the chart shows the following compared to the controls which are similar in medial/lateral loading at impact.

5° Medial Wedge 45° TurnoutLessened the medial compartment peak load
5° Medial Wedge ParallelMinimally lessened medial load
5° Lateral Wedge TurnoutLessened medial compartment load
5° Lateral Wedge ParallelMinimally lessened medial load
2.5° Lateral Wedge 45° TurnoutLessened medial load
2.5° Lateral Wedge ParallelMinimal lessened medial load
2.5° Medial Wedge 45° TurnoutMinimal lessened medial load
2.5° Medial Wedge ParallelMinimal lessened medial load
Control 45° Turnout 
Control Parallel Feet 

Medial Compartment Force Reduction: The greatest reduction in the medial compartment peak force at impact on the left knee is when the golfer turned the left foot out 45° and wore a 2.5° sloped lateral cushioned wedged insole. There is a similar peak force reduction on medial compartment when the foot it turned out and a 5° lateral cushioned wedged insole is utilized.

Lateral Compartment Force Reduction: The controls had the least lateral compartment peak forces recorded at impact. The next closest lateral reduction in lateral compartment force was with a 5° medial wedge and the lead foot in the parallel position.

Recommendations For Unloading Compartments of the Knee: The axial load is reduced across the knee at impact when the lead foot of the golfer is turned out 45°. However, other tests showed that the lateral compartment loads are higher when the foot is turned out.

Lead Knee Medial Compartment Protection: Turn the lead foot out 45° and use as 2.5° sloped cushioned lateral wedged insole.

Lead Knee Lateral Compartment Protection: Keep the lead foot parallel and consider using a 5° sloped medial cushioned wedged insole.


The loads on the knee joint in golf heretofore were not a focus of attention. Direct measurement of the loads with a novel electronic knee at the Scripps Institute showed the loads to be surprisingly high even at slow club head speeds. The presumption of higher swing speeds causing greater loads is anticipated. Results showed the benefit of use of soft spikes, Golf Specific shoe insoles to be independently effective in unloading the back knee of the right handed golfer during all phases of the golf swing.

The independent use of an unloader knee brace was not effective, but when used in combination with the Golf Specific insole reduced the force of impact on the lateral compartment of the back knee by 56%.

Turning the lead or left foot out on a right handed golfer reduced the axial load on the knee, but increase by 5% the lateral compartment load. A turned out lead foot may decrease the axial load and would be position of choice for patient with medial compartment arthritis as it also shifts forces off that compartment.

Validity of the Testing Method: Past testing of the E-Knee supports the validity and reliability of these results. Since these studies represent only one subject, the statistical significance is not possible to calculate.

Present Recommendations: It appears that the 5 Degree Wedged Cushioned Insole tested herein affords reduction in forces across the entire right or back knee of a right handed golfer and specifically the lateral compartment.

There is both a prophylactic and therapeutic wellness health application for reducing the forces across the knee joint during golf practice and play. Evidence to date would suggest the use of soft spiked shoes and this Golf Specific Insole would be a practical method of unloading the knee in this sport. The addition of an unloader knee brace to the above mentioned orthosis would have a cumulative effect reduction in the loads on the back knee lateral compartment.

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Caution: Not intended for individuals with severe foot deformities or those who suffer from circulatory diseases that result in infections or ulcerations on the bottom of the feet