Why assess Acl injury risk?

  • Prevalence/Consequences

    Female athletes are approximately three times more likely to tear an anterior cruciateligament (ACL) compared to their male counterparts (Prodromos, Han, Rogowski, Joyce, & Shi, 2007). Younger (age, 15-25 years) athletes participating in landing and cutting sports such as basketball and soccer are at greatest risk for ACL injury (Griffin et al., 2006). This elevated risk coupled with a nearly two-fold increase in female sports participation over the last 30 years (Irich, 2012; NFSHSA, 2012) has led to a rapid rise in ACL injuries in females (≈ 3 injuries per 10,000 athlete-exposures or around 1 injury per 30 individuals during a sports season). Anterior cruciate ligament surgery cost has been shown to be approximately $5,000/injury, which doesn't include the post-operative rehabilitation or lost time from work/sport (Swenson et al., 2012). In the U.S. alone, the annual cost of ACL injury likely exceeds $3 billion (Kim, Bosque, Meechan, Jamali, & Marder, 2011). Additional consequences of ACL injury include time out of sport/school, scholarship loss, significant risk for re-injury, and osteoarthritis (Ardern, Webster, Taylor, & Feller, 2011; Lohmander, Englund, Dahl, & Roos, 2007; Wright et al., 2007). Interestingly, most ACL injuries occur in a non-contact situation (Agel, Arendt, & Bershadsky, 2005; Krosshaug et al., 2007b) and are likely preventable (Hewett, Myer, Ford, Paterno,& Quatman, 2012).

  • Injury Prevention

    Neuromuscular training can reduce the relative risk for non-contact ACL injury by 73.4%. Unfortunately, the number of individuals that must participate in training in order to prevent one injury is about 108 (Sugimoto, Myer, McKeon, & Hewett, 2012). The time commitment involved in training this number of individuals is non-trivial. Moreover, the prevention techniques including physical training likely only benefit high-risk athletes (Myer, Ford, Brent, & Hewett, 2007). Administering prevention programs to the low-risk likely constitutes an inefficient use of time and resources. If training instead targeted the high-risk, the number of individuals needed to train to prevent an injury would be reduced.

  • Screening

    Anterior cruciate ligament injury risk screening tools have been identified and developed for High School age (15-19 years) female athletes using prospective 3D biomechanical analysis procedures. Specifically, 205 young (age ≈ 16 years) female athletes were screened (using 3D biomechanical motion analysis of the drop vertical jump) and tracked through two sports seasons (13 months) (Hewett et al., 2005). Knee abduction moment and angles (initial contact and peak values) were found to be significant predictors of ACL injury status for the 9 non-contact ACL injuries. Peak knee abduction moment was found to be the best independent predictor of injury status displaying sensitivity of 78% and specificity of 73%. Three-dimensional, biomechanical laboratory screening is not feasible for widespread field-based or clinical use because of the high associated cost, specialized equipment, and implementation times. However, the existing, high precision tools have provided a biomechanical risk assessment standard that can be used for validation of and comparison with alternative screening approaches.

    Visual inspection or observational movement diagnosis is one alternative screening method, which would reduce screening time and cost, while preserving relatively high-risk assessment accuracy. For example, a practitioner (i.e., coach, athletic trainer, physical therapist, etc.) could nearly instantaneously assess ACL injury risk by observing a task where movement patterns would be similar to those that cause ACL injury (i.e., jump landing, cutting, etc.). In order for this screening method to be valid, skill must be assessed. You can test your injury risk prediction skill here where you will recieve feedback regarding your test performance compared to verified experts from North American and Europe.