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Anterior Cruciate Ligament (ACL) Injury & Prevention

ACL Injury Prevelance: 

Injury to the Anterior Cruciate Ligament (ACL) is extremely common.  It is estimated that athletes sustain 200,000 of these injuries each year in the United States, and that between 1 in 50 to 100 youth athletes will rupture their ACL during a sports season.  Despite the commonality of ACL tears, they are actually very serious injuries with the potential for both short and long term pain and disability.  

How is the ACL Injured?

The ACL is the primary ligament stabilizer in the knee.  It prevents the tibia, or shin bone, from sliding and twisting out from under the femur, or thigh bone.  The majority of injuries to the ACL occur from a non-contact injury.  A sudden deceleration, cut, pivot, or landing from a jump is all that it takes to rupture the ligament.  Soccer, volleyball, basketball, softball, football, and skiing have some of the highest rates of ACL injury. It takes only 40 milliseconds for an ACL rupture to occur, which is much too quick for an athlete to consciously adjust their leg and body to prevent the injury.  

Why ACL Injuries are a Big Deal:

Injury to the ACL results in both short and long term disability.  ACL injury is quite painful, and in youth athletes, almost always requires surgery to reconstruct the torn ligament.  Youth athletes are guaranteed to miss school and sports seasons.  Injured youth athletes can become alienated from friends and teammates, and this separation from peers has been shown to lead to higher rates of depression and poor school performance.  These injuries are also costly, with the average lifetime surgery and rehabilitation costs nearing $40,000.  Even if a youth athlete makes a complete recovery in the short term, the problems in the long term are even more daunting.  Even athletes who have a surgical reconstruction of the ligament have a 40-70% chance of developing osteoarthritis of the knee within 15 years.  

The perception in many people’s minds is that rehabilitation from an ACL injury will result in a complete return to sport.  This perception is influenced by elite athletes who return from ACL surgery to achieve sport excellence.  Adrien Peterson, who tore his ACL and then returned to set the NFL single season rushing record and Lindsey Vonn, who tore her ACL twice but returned to win multiple World Cup Downhill events are two prime examples.  However, the orthopedic surgery literature tells a different story.  The most recent cumulative study on return to sport after ACL reconstruction demonstrated only 63% of athletes will attain their pre-injury level of athletic function.  Even worse, only 44% of athletes will actually return to competitive sport

Risk of Sustaining an ACL Tear:

The Education Amendments of 1972, also known as Title IX, was a huge development for women’s sport equality.  This act resulted in significantly greater numbers of youth and adolescent girls participating in organized sports.  By the early 1990s, the orthopedic surgery literature had made clear that this increase in girl sport participation had resulted in a significant number of knee injuries in girls.

Subsequent data has shown that girls have up to an 8 times risk of sustaining ACL injury when compared to boys.  Multiple factors are responsible for this increase risk.  Compared with boys, girls have smaller ligaments, less fast twitch muscles, hormones that make their ligaments more loose, and higher risk leg alignment due to their wider hips and more “knocked” knees.  Girls also tend to land jumps using their quadriceps more than their hamstrings, collapse their knees as they cut or land, and rotate their center of gravity more than boys.  As opposed to the genetic and biologic differences that are not modifiable, researchers began to study ways to lessen ACL risk by improving on girls neuromuscular function.  

How to PREVENT an ACL Injury:

Since the mid 1990s, researchers have studied more than 60 different exercise, strength, balance, and movement programs in an attempt to lessen the risk of ACL injury.  Over 600 peer reviewed studies in the orthopedic and sport performance literature have demonstrated that neuromuscular training can significantly reduce the risk of sustaining an ACL injury.  These programs actually decrease the risk of all knee and ankle injuries.  A secondary benefit of these programs is that they lead to improvements in athletes sport performance including improvements in vertical jump, speed, agility, aerobic fitness, single leg hop, and hamstring and quadriceps strength.  

The Flagstaff Sports Institute utilizes the most current scientific and sports performance literature to develop programs to both decrease the injury risk of our Flagstaff Youth athletes and also to maximize their sports performance.  


  • Ardern CL.  Return to sport following anterior cruciate ligament reconstruction surgery:  a systematic review and meta-analysis .  Br J Sports Med.  2011
  • Societal and Economic Impact of ACL Tears.  Mather R, MOON Knee group.  JBJS.  2013
  • Westin, B.    ACL Injury Prevention Training in Female Athletes.  Sports Health.  Feb. 2012
  • Barber -Westin S.  A Training Program to Improve Neuromuscular and Performance Indicies in Femal High School Basketball Players.  J of Strength and Conditioning Research.  March 2012. 
  • Noyes FR.   Neuromuscular Retraining in Female Adolescent Athletes.  Sports 2015