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Landing characteristics in women may cause more ACL damage
Researchers discover that left jumps could increase ligament ruptures.
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HOLLYWOOD, Fla. — Physicians have known that women incur more non-contact ACL injuries, but the reasons for this remain unclear. A recent study indicates that the higher rates may be related to the way women land after jumping.
Based on analysis of the right knee landing kinematics and kinetics during different jump directions, researchers found that jumping to the left created more knee valgus and shear force, therefore, placing all participants at a higher risk for ACL injuries. They also determined that women landed in more valgus positions during the left jumps.
“In addition to the differences observed in the jump direction, we demonstrated that females exhibit different landing kinematics during the most hazardous of these jumps, which may indicate or provide evidence for their increased risk of injury during these types of tasks,” said Timothy C. Sell, PhD, PT, during his presentation at the 2005 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. The research won third place for the John Joyce award.
To examine movements similar to those implicated in noncontact ACL injuries, researchers observed 18 male and 17 female healthy basketball players. Participants performed jump-landing tests, which included landing with both feet, switching direction and fast deceleration, said Sell, a post-doctoral research fellow at the University of Pittsburgh Medical Center. The players jumped right, left and vertically. Researchers assessed knee flexion and valgus angles, tibia shear force and valgus moment with each direction. They performed motion analysis and inverse dynamic calculations to determine joint position and force, he said.
Gender differences
Investigators discovered that left jumps were the most dangerous for all participants. “Jumping to the left, individuals landed in greater valgus; greater than the straight vertical jump and significantly greater than the jump to the right,” Sell said. The direction created more shear force and less knee flexion (both P < .001), researchers said in their abstract. Left maneuvers also demonstrated the greatest valgus moment (P = .001), they reported in the abstract.
Women landed in more dangerous positions during the left jumps. “Females tended to land in a valgus position compared to males who landed in either a neutral or slightly varus position,” Sell said. In addition, researchers found that women landed with more extended knees, he said.
The findings build on established knowledge about ligament damage. “We know that jumping and landing with the knee in extension greatly increases ACL strain,” Sell said. “In addition, landing in the valgus position has been recently identified as a risk factor for non-contact ACL injuries. And finally, combining a valgus moment with a proximal anterior tibia shear force can increase ACL forces much greater than proximal anterior tibia shear forces alone.”
For more information:
- Sell TC, Ferris CM, Abt J, et al. Females demonstrate unsafe landing kinematics during lateral jump landing tasks implicated in noncontact ACL injuries. #118. Presented at the 2005 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. April 3-7, 2005. Hollywood, Fla.