As summer fades away and signs of fall begin emerging, we also begin to see an increase in the number of knee injuries, especially ACL tears. Everyone who watches professional and college football has likely seen a player tear an ACL. A player gets hit in the knees or hard enough above the knees with his foot planted on the ground, he falls to the ground grabbing his knee and his season is over.
There are 2 causes of ACL tears: Contact and Non-Contact. Contact ACL tears are often seen in football and involve some type of external force; whereas non-contact occur with a quick change in direction and do not involve a hit from another player. ACL tears in football often include both, whereas the majority of other sports typically see non-contact ACL tears.
Approximately 100,000 – 200,000 ACL injuries occur per year1, many of those happen to high school and college athletes. Non-contact injuries account for approximately 70% of all ACL tears2 with females being up to 8 times more likely than their male counterparts to endure an ACL tear3. So what makes some athletes and more specifically females more likely to tear their ACL?
First, it is important to understand the ACLs function and the mechanism that often leads to injury. The ACL is a ligament that runs diagonally and connects the upper leg (femur) and lower leg (tibia). The ACL prevents the tibia from moving anterior or forward of the femur and also resists rotational movement. When the tibia is forced to move forward and rotated (think of making a sharp turn while running), the ACL is stressed. If that stress is too much for the ACL, it will tear.
Non-contact ACL tears are more likely to occur during sharp cutting, jumping, or an unexpected and sudden change in direction. When the knee is placed in a valgus (knock kneed) position while performing above mentioned activities, the ACL is placed under tremendous stress and is much more likely to tear. Certain athletes are more susceptible to this position, making them more likely to sustain an ACL tear.
Some of the most likely factors contributing to ACL tears involve anatomical differences between males and females; weakness of hip muscles; and poor neuromuscular control which includes poor balance and movement patterns. Females often have wider hips, which contribute to their knees being in a valgus or "knock knee" position with the knees inside of their hips and feet.
Many athletes have weakness of hip muscles specifically their glute maximus and medius. A weak glute medius will also contribute to a valgus knee position. This can often be addressed through proper strengthening programs as well as programs that address movement dysfunction and posture abnormalities.
Lastly, poor neuromuscular control contributes greatly to ACL tears. Many athletes have poor balance and do not know how to squat, jump, land, or even run properly. Much of this is also due to poor body awareness. When performing any of these motions, it is vital that the knee does not move inside or forward of the foot. Many ACL prevention programs are geared towards addressing neuromuscular deficits and movement dysfunction which includes addressing strength and flexibility issues, and training athletes to jump and land correctly. If athletes cannot jump or land correctly while training, they will not land correctly when going up for a head ball, rebound, or spike.
If you are a parent of an athlete, try these two tests. First, have your child jump fairly high a couple of times. Watch their knees as they jump and land. Do their knees move close together, inside of their big toe? Are their knees nearly touching? Are their knees going in front of their toes? Second, how deeply they can squat? Can they squat so their thighs are AT LEAST parallel to the ground while keeping their heels flat and knees over their toes? (ideally they should be able to fully squat). If they cannot perform both of these successfully, I would absolutely recommend a good ACL prevention program to address the dysfunction and teach/ train proper movement.
ACL Prevention programs are often run by athletic trainers, physical therapists, and strength coaches who teach proper technique and fix movement dysfunction. ACL tears are common among all levels of sports. Although preventing all ACL tears cannot be guaranteed, teaching proper technique and movement patterns will greatly help reduce the chance of non-contact ACL tears.
Good luck for a healthy and fun Fall.
- Gordon M, Steiner M. Anterior cruciate ligament injuries. In: Orthopaedic Knowledge Update Sports Medicine III, Garrick JG. (Ed), American Academy of Orthopaedic Surgeons, Rosemont 2004. p.169.
- Boden B, Dean G, Feagin J, et al. Mechanism of anterior cruciate ligament injury. Orthopedics.2000; 23: 573-578.
- Arendt E, Dick R. Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature. Am J Sports Med. 1995;23:694–701