The anterior cruciate ligament, or ACL, connects the thighbone to the shinbone in the middle of the knee and prevents the shinbone from moving too far forward (excessive anterior translation of the tibia on the femur). It also prevents excessive internal rotation of the tibia and hyperextension of the knee, according to the National Academy of Sports Medicine.
(adapted from here)
A front-page article in today’s Chicago Tribune underscores the importance of taking care of the ACL while participating in high school sports, not just in treating injuries to the ligament after they occur.
“Traditionally, we’re really good at doing these things following the injury,” the Tribune quoted Mike Sullivan of the Illinois Athletic Trainers Association as saying. The association recently came out with its own protocol. “Finally we realized that if it works after the injury, why don’t we do it before it happens?”
How does the ACL get torn?
ACL injuries are about two to six times more common in girls’ sports than they are in boys’ sports, the Tribune noted, comparing the per-exposure injury rates for several sports across the country.
Studies spanning decades have shown higher injury rates for girls than boys, so that fact alone isn’t news. “The knee injury rates for girls’ basketball and girls’ soccer were higher than for their male counterparts,” wrote John W Powell and Kim D Barber-Foss, here, back in 2000.
Because of the way girls jump and the fact that one leg is typically stronger than the other, they have a harder time than boys keeping their ACLs free from injury.
A 1999 article, published in the Journal of Athletic Training, explained the underlying mechanism for ACL injury in sports by analyzing photographs. In cases where the injury doesn’t result from contact, the ligament is typically injured upon landing from a jump or upon rotating the knee to a “position of no return” in a move like trying to stay in bounds with the ball, writes Mary Lloyd Ireland of the Kentucky Sports Medicine Clinic.
The position of no return means flexing the knee much less than it would be in a safe position and landing on one foot, out of control. A safe position means landing on two feet with control and distributing weight in a balanced way on the middle of both feet, not just on one foot and not just on the ball of that foot.
After studying the mechanism for several decades, athletic trainers and doctors are now trying to teach girls how to land and maneuver in order to avoid tearing their ACL. Don’t get me wrong: boys have the same “position of no return,” but the difference in muscle strength between one leg and the other in girls and the fact that girls tend to jump using their quadriceps while boys jump using much more of the hamstrings make it more likely girls will land in an unsafe position after they go up for a jump.
Unless they can be trained to jump, land, and rotate in safer positions.
“A primary goal in treating athletes is prevention of the injury. We cannot restore an ACL-injured knee to normal with a reconstruction. Analyzing data collected from multiple centers and large numbers of athletes over time will allow us to identify high-risk individuals early and to institute appropriate intervention programs,” Dr Ireland concluded.
So how are we training girls to avoid ACL injuries?
Since girls tend to have less neuromuscular control of their knees than boys, they need more conditioning. The Knee Injury Prevention Program, or KIPP, from the Ann & Robert H Lurie Children’s Hospital of Chicago, provides about 20 minutes of explosive jumping, specialized warm-ups, and strengthening drills for girls.
It seems to work. Dr Cynthia LaBella, medical director for the hospital’s Institute for Sports Medicine, said in a study involving Chicago Public Schools students, those participating in the KIPP showed a dramatic reduction in the rate of ACL injury, compared to girls who didn’t incorporate the program in their training.
Many other programs can be found in the literature as well (see here and here, for example). All of them focus on screening for predisposition to ACL injury and training of some sort in biomechanics. In other words, prevention programs aim to teach girls how to jump and land in order to prevent ACL injuries in the first place.
“Doing this over and over makes this a reflex in an athlete,” Dr LaBella was quoted as saying. “They’ve done it so many times they’ll do it naturally on the court.”
What is your school team doing to prevent ACL injuries?