ACL Injuries and the Tale of the Tape
Video Analysis of Anterior Cruciate Ligament Injury: Abnormalities in Hip and Ankle Kinematics. Barry P. Boden, Joseph S. Torg, Sarah B. Knowles and Timothy E. Hewett. The American Journal of Sports Medicine, 37 (2) 2009
In spite of the growing mountain of reports and analyses concerning ACL injuries, the researchers in this study felt that "the mechanisms of noncontact anterior cruciate ligament (ACL) injury have not been clearly defined." Researchers were most interested in foot position and lower extremity joint angles of athletes at the time of ACL injury. They hypothesized that "compared with uninjured athletes performing comparable athletic maneuvers (controls), athletes with ACL injury (subjects) would show a more flatfooted profile and a more flexed hip at landing after a jump or after a sharp deceleration maneuver."
They reviewed videotapes of ACL injuries to athletes, gathered over a 12-year period (1995-2007) from the NBA and WNBA, physicians, athletic trainers and patients. Of the 70 videotapes considered, 29 videos were analyzed. Researchers chose videos that showed non-contact ACL injuries to athletes (defined as minimal contact with other athletes, no direct contact with the knee, no tackling or shoving by an opponent) as well as clear footage of the athlete's foot contacting the ground. Sports represented in the tapes were a mixture of professional, college and high school sports including basketball, handball, soccer, football, competitive cheerleading and gymnastics. These 29 "subject/injury" videos were then compared with a "control" group of 27 videos showing professional and collegiate basketball players "performing similar decelerating or landing maneuvers during game situations."
Researchers studied video of jumping athletes as their feet made contact with the ground after a jump and noticed that the forefeet of the control group athletes contacted the ground first, while athletes of the injury group had "first ground contact with the hindfoot or entirely flatfooted, attained the flatfoot position significantly sooner, had significantly less planter-flexed ankle angles at initial contact, and had a significant larger mean hip flexion angle." Researchers concluded that jumping athletes who touch down flatfooted or with the hindfoot may have a higher risk of ACL injury.
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