Spoiler alert: Soccer cleats shouldn’t be worn on artificial turf.
Sorry for killing the suspense of this article, but this research is too important to beat around the bush. Coaches, parents and players please read on and please share this information.
I have been seeing an increase of serious knee injuries in youth soccer recently. Two national level teens in my area saw their soccer dreams put in jeopardy because of serious knee injuries. What struck me is both of these girls were in amazing condition. Both have very athletic physics and looked as though they could easily handle the physical nature of playing on any boys’ team. In fact they frequently did! So seeing these two players in tears as they clutched at their knee was very unexpected and heart breaking. What made it even more unexpected is both injuries happened in non-contact situations wearing cleats on turf while doing simple maneuvers they’ve probably done thousands of times.
Non-contact knee injuries in soccer are on the rise. In fact, the increase is startling… The number of children needing ACL reconstructions has more than tripled the past 15 years! The increase is even more pronounced in teenage girls. There are many theories as to why ACL injuries are increasing, and even more theories as to why the number ACL injuries in teenage girls are rising. I’ll address some of those theories a bit further in this article. Let’s first understand the anatomy of the knee and what circumstances can cause an injury to ligaments of the knee.
- The knee is one of the largest and most intricate joints in the body. The knee links the thigh bone (femur) to the shin bone (tibia). The smaller bone that runs alongside the tibia (fibula) and the kneecap (patella) are the other bones that create the knee joint.
- Tendons connect the knee bones to the muscles that move the knee joint. Ligaments join the knee bones and provide stability to the knee joint.
- The A.C.L. (anterior cruciate ligament) stops the femur from sliding backward on the tibia (or the tibia sliding forward on the femur).
- The posterior cruciate ligament prevents the femur from slipping forward on the tibia (or the tibia from sliding backward on the femur).
- The medial and lateral collateral ligaments prevent the femur from moving from side to side.
- Two pieces of cartilage called the medial and lateral menisci are shock absorbers between the femur and tibia.
- Numerous bursae, or fluid-filled sacs, help the knee move smoothly.
Why females are more susceptible to knee injuries
Numerous research studies that have been conducted indicate that females are more vulnerable to knee injuries. In fact, most believe that females are a staggering 4 to 9 times more likely to tear their ACL as compared to men. There has been much discussion and debate to exactly why this is the case. Most common conclusions are:
- Structural differences in the knee such as the smaller length of the ligaments and more laxity.
- Alignment of leg and knees because of widening of female pelvis in preparation for child birth. This causes an inward angle of the Femur (thigh bones) which some believe can cause more pressure on the inside of the knee and cause the knee to bend inward.
- Quadricep/Hamstring strength ratio: Woman have weaker hamstring muscles and cannot balance out the stronger quadriceps muscle. Thus putting additional strain on the ACL.
The exact reason for this difference is beyond the scope of this article. What is important to note is that the research conclusively shows a higher risk of knee injuries for female athletes.
How a knee injury typically happens
A sprain is a stretched or torn ligament. There are three grades of sprain, a grade one is a partial tear and grade three is a complete tear. When a ligament is torn the chief complaint is usually a “buckling” sensation in the knee. The reason for this is the ACL’s major role is providing stability to the knee.
Knee injuries typically are a result of a fast movement with a degree of rotation and pivoting involved. The foot and lower leg turn outward, comparative to the upper leg turning inward, generating a gapping force on the interior of the knee. This is usually called a valgus force. Players with hip control issues are considered to be more susceptible to an uncontrolled valgus force. The knee valgus strain and hip internal rotation strain combined has been shown to increase the strain on the ACL with enough force to cause it to rupture. What does this exactly mean? I have included a video that explains the conditions for a knee injury in a much simpler way.
How a soccer cleat contributes to the possibility of a knee injury
A research paper spearheaded by Orthopedic Surgeon Mark C. Drakos, MD, and published by The American Society of Mechanical Engineers sought to evaluate the impact of various cleats on various surfaces. The process of evaluating these variations was quite intricate and well executed. You can find the study here (Link), if you are interested in reading more about their methods and findings. The study produced two interesting results: The first is that the safest shoe/surface combination is a traditional soccer cleat on grass. That’s reassuring as a large majority of youth games are played on grass. The second finding is the critical one: The worst combination was a traditional cleat on turf.
The Journal of the Academy of Orthopedic Surgeons also published research (Link) on the subject. Again Dr. Drakos was on the research team. The article points out: “Optimal shoe-playing surface conditions may be level and sport-specific,” said orthopedic surgeon and lead study author Mark C. Drakos, MD. “The shoe-playing surface interface is a modifiable risk factor for injury, and further research is needed to improve playing conditions for athletes of all levels.”
Two additional major findings were:
- Most types of shoes have higher peak torque (foot movement and movement force) on artificial turf than on natural turf.
Sole material and cleat pattern and shape may affect torque. For example, shoes with small cleats place the lowest amount of pressure on the foot, and may potentially minimize the incidence of foot stress fractures on artificial surfaces.
- The research clearly pointed out that shoes with smaller cleats and higher in quantity put less strain on the knee joint. The good news is this is consistent with turf shoes designed for soccer that are currently on the market from Adidas, Nike, Puma and most major soccer shoe manufacturers.
After reviewing these findings, I reached out to Dr. Stuart C. Hui, D.C., ATC/L of Paradigm Performance Center in Elgin Illinois, a suburb of Chicago. Dr Stu has a degree in Kinesiology, Doctorate in Chiropractic studies, National Board Certified in Athletic Training and Chiropractic, also certified in: Cox flexion-distraction technique, Acupuncture, Applied Kinesiology, Sole Support Orthotic casting and evaluation, Z Health Performance Systems and Advantage Golf Fitness Instruction and finally served as an acupuncture specialist for the Chicago Fire Soccer team.
He works with elite athletes every day. So, needless to say I was eager to get his input on these findings. Dr. Stu agreed with the research and the findings of the articles and added that not only does the number of spikes and depth contribute to the problem, but also the materials of the shoes themselves play a big part in preventing knee injuries. He stated that the more rigid the sole of a soccer shoe the more likely it puts additional strain on the knee joint. The same goes with the upper part of the shoe. He pointed out shoes made with natural leather are much more flexible and allow the cleat and foot to rotate more easily allowing the twisting force on the knee to be decreased.
Conclusion: Research indicates a significant increase in the chance of a knee injury when wearing traditional cleats on artificial turf. We at SoccerHotSpot believe that traditional cleats shouldn’t be allowed on artificial turf anymore. The use of “turf shoes” seems especially important for female players as statistics indicate they are predisposed to have a greater chance of ACL injuries. When choosing soccer shoes for artificial turf choose one with a many cleats that are shorter like the one pictured above. Also, find a shoe that has a flexible sole and upper. Keeping these factors in mind when you buy soccer shoes for turf will greatly decrease the chances of a knee injury. Most of the major soccer shoe manufacturers have turf shoes that have these characteristics.
It is up to players, parents and coaches to share this information and hopefully US Soccer will follow suit and ban soccer cleats on artificial turf in youth soccer.
Important note: Dr Stu was adamant about advising me that he has noticed a disturbing trend in today’s young athletes and the way their issues are presenting themselves. Notably he is seeing “a lack of basic human function in our hips and lower extremities. He says today’s “screen based society” is sitting down much more than our bodies are designed to withstand. This lack of correct movement is creating significant issues that are robbing athletes of flexibility and explosiveness, thus preventing elite competitors from reaching their full potential.
I plan on pursuing this subject further with Dr. Stu for a future article. If you are interested in this article, pleases subscribe to our blog and we’ll make sure you are notified as soon as it’s posted.
To learn more about Dr. Stu and Paradigm Performance Center visit their website click here: http://www.drstuarthui.com
Or follow Dr. Stu on Facebook here: https://www.facebook.com/train2performusa/
Below is an inspiring video by US Soccer Star Ali Krieger. She tore her ACL and has since learned hot to avoid these injuries in the future. She also shares some great advice in exercises that help prevent ACL injuries.
5 best Turf Shoes to Buy: We feel these shoes best represent the features we mention in the article; Soft sole, flexible upper, and of course many shallow round spikes. – SoccerHotSpot