Effects of Playing Surface and Shoe Type on ACL Tears in Soccer Players

Today, Anterior Cruciate Ligament (ACL) tears are one of the most prevalent knee injuries, with the occurrence of ACL tears increasing drastically from approximately 80 000 in 2000 to 150 000 in 2011. Although there are many factors that contribute to an ACL tear occurring, certain environmental factors could contribute to the dramatic increase over the past couple decades, especially in athletes. This study explores two of these possible factors; the playing surface and the type of shoes worn by soccer players. The effects these factors have on ACL tears were evaluated by measuring the maximum torque achieved prior to the shoe breaking free of the playing surface using a servo-hydraulic bi-axial load frame. A prosthetic foot fitted into various soccer shoes was fixed to the load cell and different playing surface samples were fixed to the actuator of the load frame. Axial loads were applied to simulate an athlete's body weight and rotations were applied to simulate an athlete pivoting on that playing surface. The maximum torque achieved prior to the soccer shoe slipping on the playing surface was measured. Out of the shoes tested, this investigation finds that wearing round study cleats or turf shoes on artificial turf surfaces provides the best traction for maneuvers in games while still allowing the shoe to slip when more dangerous torque levels are reached. Additionally, grass surfaces were found to be safer than artificial turf surfaces, as grass has the ability to deform or break to maintain a threshold torque value, making it less likely for the torque to reach higher values associated with ACL injury.