Grass and Cleats Combo May Be Best for Knees

< Feb. 03, 2010 > -- Shoes and the type of surface you're playing on make a difference in your chances of injuring a knee during sports, according to a new study. A combination of natural grass -- rather than artificial turf -- and cleats seem to be the best combination. 

Overstretching or tearing the anterior cruciate ligament (ACL) in the knee is common among athletes, particularly women. Often to blame are activities that require quick stops and turns, such as basketball, football, soccer, and skiing. 

These injuries commonly occur when an athlete plants a foot while making a quick turn, says Mark Drakos, M.D., co-author of the study that appears in the January issue of the Journal of Biomechanical Engineering.

"As a former football player, I was always curious about why I was more sore after playing on artificial surfaces than playing on grass, and I wanted to find out the reasons behind that using a biomechanical model," Dr. Drakos explains.

Grass and Cleats Result in Less Force

Researchers used lower extremities -- knee, foot and ankle -- from cadavers to test the strain placed on the ACL by four different combinations of shoes and playing surfaces:

• Turf shoe and Astroturf
• Turf shoe and modern playing turf
• Cleat and modern playing turf
• Cleat and natural grass
  

When a similar quick turn was made with all four combinations, cleats on grass created the least force on the knee ligament, according to Dr. Drakos.

Compared with the natural grass/cleat combination, the Astroturf/turf shoe put 80 percent more strain on the ACL. Strain was 48 percent greater with the modern playing turf/turf shoe, and 45 percent more with the modern playing turf/cleat combination.

"We don't know all the science behind why ACL injuries may be more common on turf than on grass," says Dr. Drakos. "I think it is a scenario that deserves attention and further research."

Contact and Non-Contact Sports Can Cause Injury

There are 200,000 ACL injuries every year in the U.S. alone, according to Dr. Drakos. ACL tears may result from either contact or non-contact injuries.

A blow to the side of the knee, which can occur during a football tackle, can cause an ACL tear. Coming to a quick stop, combined with a direction change while running, pivoting, landing from a jump, or overextending the knee joint also can cause injury to the ACL.

Symptoms of a stretched or torn ACL include:

• A "popping" sound at the time of injury
• Swelling around the knee within six hours of injury
• Pain, especially when you put weight on the injured leg
  

If the injury is mild, you may only notice the knee "gives way" or feels unstable at the time of injury.

What to Do for an Injured Knee

You're playing soccer when suddenly you make a sharp turn and hear your knee "pop," indicating an anterior cruciate ligament (ACL) injury. If this occurs, you can take measures to alleviate pain and stabilize the injury:

• Elevate the knee above heart level
• Apply ice
• Use over-the-counter pain relievers such as nonsteroidal anti-inflammatory (NSAID) drugs 
  

If you've injured your knee, see a doctor before playing again. You may need crutches to walk until the swelling and pain have improved. Physical therapy can help you regain joint motion and leg strength.

In the case of a serious knee injury, do not move the joint. Keep the knee straight with a splint until a trained medical professional has evaluated it. Such injuries may require surgery to construct a new ACL.

If the foot is cool and blue after a knee injury, you may have dislocated the knee and injured blood vessels to the foot. Seek immediate professional help.

Always consult your physician for more information.