"These are injuries where an athlete plants his or her foot while making a cut and blows out his or her knee," Dr. Mark Drakos, a study co-author who, at the time of the research, was an orthopedic fellow in sports medicine at the Hospital for Special Surgery in New York City, said in a hospital news release. The ligament is commonly referred to as the ACL.

"We don't know all the science behind why ACL injuries may be more common on turf than on grass," Drakos said. The study begins to address that, he said, because "we need to optimize some of those environmental factors.

To that end, the researchers used lower extremities -- knee, foot and ankle -- from cadavers to test the strain placed on the ACL, one of four major ligaments in the knee, by four different combinations of shoes and playing surfaces: turf shoe and Astroturf; turf shoe and modern playing turf; cleat and modern turf; and cleat and natural grass.

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

When a similar cut, or quick turn, is made on four different surfaces, "the best strain profile is in grass/cleat combinations," Drakos said. "So, there is less force occurring at your ligament for the same cut on that particular surface using this model."

The finding is published 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," Drakos said.

"There are basically 200,000 ACL injuries every year in the United States alone, and this [type of playing field and type of shoe] is an environmental factor which has been shown to play a role in injury, but has yet to optimized," he said. "I think it is a scenario that deserves attention and further research."

More information

The U.S. National Library of Medicine has more on ACL injury.

SOURCE: Hospital for Special Surgery, news release, Jan. 20, 2010

-- Robert Preidt