The ACL is a primary stabilizer of the knee joint. It is a rubber bandlike fiber no bigger than your pinkie. It runs through the center of the knee joint, attaching the thighbone (femur) to the shinbone (tibia). A tear can be a devastating injury to any athlete, involving many months of rehabilitation.
While sports like jogging, swimming and biking place little stress on the ACL, sports such as soccer, basketball and volleyball that involve cutting, planting and changing direction put athletes, particularly females, at greatest risk of ACL injury.
Multiple studies have set out to discover why women are more likely to tear their ACL than men. Scientists cite anatomical differences, such as a woman’s wider pelvis, which makes her thighbones angle downward more sharply than a man’s (the so-called Q angle) creating a knock knee tendency in women.
Some studies point to the relationship between the intercondylar notch (the groove in the femur through which the ACL travels) and ACL injuries, concluding that the smaller notch width in women is to blame. Hormones have also been named as culprits since estrogen affects the laxity or looseness of the joints. Greater joint laxity means greater stress on the ligaments.
While noteworthy, these numerous studies are not particularly helpful to women since they do not point to any obvious ways of preventing the injury, short of changing their anatomy or biochemistry.
Although we cannot do this, we can, however, help change the way girls and women move. The good news about ACL tears is that 70 percent are noncontact injuries, in other words, they don’t involve an outside force such as an opposing player, goalpost or another object on the field or court. ACL injuries appear to occur most frequently during deceleration activity such as a sudden stop, change in direction or landing from a jump. Both are factors that can be influenced substantially through functional (not sport-specific) training, which emphasizes quality of movement and builds form, flexibility and strength.
At The Stone Clinic, we recommend jumping and landing training, with a focus on landing with the knees in neutral position over the feet. This exercise, when combined with squats, is the best combination for lower extremity training and injury prevention.
While ACL injuries in women show no sign of slowing down, newer methods of ligament and cartilage repair, regeneration and replacement may make the consequences of those previously debilitating injuries much less severe. At The Stone Clinic, we have developed novel ways of replacing a damaged ACL using donor tissue, following strict guidelines about what type of tissue to use. We no longer use the patient’s own hamstring, which can leave them slightly weaker in knee flexion.
We also add growth factors and stem cells to diminish the impact of an ACL injury and speed healing. These techniques are also critical to our success in revising failed repairs or reinjured ACLs. More than 90 percent of our patients are able to return to full sports with a stable knee. The data is overwhelming that no matter how young the patient, ACL injuries should be repaired or reconstructed as soon as possible, to prevent the damage to the meniscus and articular cartilage that comes from an unstable knee.
Dr. Kevin R. Stone is an orthopedic surgeon at The Stone Clinic and chairman of the Stone Research Foundation in San Francisco. He pioneers advanced orthopedic surgical and rehabilitation techniques to repair, regenerate and replace damaged cartilage and ligaments. For more info, visit www.stoneclinic.com.