ACL Injury Rates (not meniscus or MCL) Are Higher In Female Athletes Than Males

This week’s EXSS Impact post was developed by Laura Stanlty (PhD student in the HMSC Doctoral Program.  This work was done in collaboration with Zack Kerr, PhD and Tom Dompier, PhD, ATC form the Datalys Center.  Many thanks to all for contributing to this week’s EXSS Impact post.

stanley1Why did you do this study?

Knee injuries are among the most commonly reported sport-related injuries at both the high school (HS) and collegiate level.1,2 When a young athlete sustains a traumatic knee injury, such as an anterior cruciate ligament (ACL) rupture, the athlete faces immediate restrictions in sport participation and must commit to lengthy, challenging rehabilitation in order to return to a high level of physical activity. With the increasing volume of youth sports participation for both males and females in recent years, there has been a steady increase in the number of traumatic knee injuries and subsequent surgeries, including ACL reconstructions and meniscal repairs.3,4 Returning to one’s prior level of activity is not always easy, nor is maintaining a competitive athletic career. In fact, a recent study by Rugg et al.5 found that fewer than 20% of collegiate athletes with a history of an ACL reconstruction were able to complete a 4-year competitive collegiate career. Unfortunately, there are also lasting concerns, as individuals suffering traumatic knee injuries are at a high risk of a future knee injury, as well as the early development of post-traumatic knee osteoarthritis.6,7,8 These consequences have ramifications on healthcare economics, other health conditions, and patient quality of life.

stanley2Over the last decade, the sports medicine community has been focused on developing and implementing evidence-based injury prevention programs. Many of these programs have been shown to be effective at improving movement-related injury risk factors, but not necessarily at decreasing the incidence of ACL injuries.9 Additionally, female athlete are often targeted in injury prevention efforts due to the higher incidence of ACL injuries among females compared to males. In order to evaluate the efficacy of current injury prevention programs, it is important to understand the current landscape of knee injury epidemiology, including updated comparisons between sexes, sports, and levels (HS and collegiate). To date, most epidemiological studies have only looked at one type of knee injury at a time. However, our study is the first to make numerous direct comparisons for three common traumatic knee injuries in the same populations during the same time period, including ACL, meniscal, and medial collateral ligament (MCL) injuries.

stanley4What did you do and what did you find?

For this study, we were able to evaluate knee injury patterns from three years of HS and five years of NCAA data reported by athletic trainers from participating schools. We chose to include sports that all involved jumping/landing, cutting, and pivoting actions (basketball, soccer, lacrosse, ice hockey, baseball/softball), as these are all movements that may place the knee stabilizing structures in vulnerable positions.

A key finding is that there is a persistent sex difference in ACL injury rates, with females approximately 2 times as likely than males to suffer an ACL injury at both the HS (IRR: 2.30) and collegiate (IRR: 2.49) levels. From the NCAA sports, women’s soccer and men’s lacrosse had the highest ACL injury rates, while at the HS level, lacrosse had the highest rates for both girls and boys. Compared to previous literature reporting ACL injury rates in NCAA soccer and basketball (Arendt & Dick, 1995), our study found that ACL injury rates have decreased overall. Our findings at the HS level are similar to previous research.

Expectantly, male athletes had an overall higher MCL injury rate, which is likely attributed to the high reported rates in collegiate ice hockey. Ice hockey at the collegiate level allows open body checking, which may increase player exposure to contact injuries through high valgus forces applied to the knee. Interestingly, there were no distinct sex differences found with meniscal injuries, although the majority of meniscal injuries were reportedly sustained during practice versus competition for both sexes at both competitive levels. Soccer had the highest sport-specific meniscal injury rate at both the HS and collegiate level. Literature describing the epidemiology of isolated meniscal injuries is limited, as it is common for the meniscus to be injured concomitantly, such as with an ACL rupture. This is an important area for more specific injury surveillance, due to the important function of the meniscus to provide stability to the knee and protection of underlying articular cartilage.

stanley3How do these findings impact the public?

A current understanding of athletic injury epidemiology is important to athletes, coaches, parents, and healthcare providers (physicians and rehabilitation specialists) alike. With regards to traumatic knee injuries, knowledge of incidence rates of common injuries aids in developing injury prevention programs, and our findings help delineate the most at-risk populations. Additionally, our findings support the need for continued efforts to develop evidence-based rehabilitation programs that minimize the risk of subsequent acute re-injuries and maintain long-term knee joint health. As interest in both preventing and treating traumatic knee injuries continues, our findings will hopefully serve as a baseline for future research examining time trends in injury rates at both the HS and collegiate levels.

References:
  1. Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and recommendations for injury prevention initiatives. J Athl Train. 2007;42(2):311-319.
  2. Ingram JG, Fields SK, Yard EE, Comstock RD. Epidemiology of knee injuries among boys and girls in US high school athletics. Am J Sport Med. 2008;36(6):1116-1122. doi:10.1177/0363546508314400.
  3. Mall N, Chalmers PN, Moric M, et al. Incidence and trends of anterior cruciate ligament reconstruction in the United States. Am J Sports Med. 2014:2363-2370. doi:10.1177/0363546514542796.
  4. Abrams GD, Frank RM, Gupta AK, Harris JD, McCormick FM, Cole BJ. Trends in meniscus repair and meniscectomy in the United States, 2005-2011. Am J Sport Med. 2013;41(10):2333-2339. doi:10.1177/0363546513495641.
  5. Rugg CM, Wang D, Sulzicki P, Hame SL. Effects of prior knee surgery on subsequent injury, imaging, and surgery in NCAA collegiate athletes. Am J Sport Med. 2014;42(4):959-964. doi:10.1177/0363546513519951.
  6. Paterno M V, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of Second ACL Injuries 2 Years After Primary ACL Reconstruction and Return to Sport. Am J Sports Med. 2014;42(7):1567-1573. doi:10.1177/0363546514530088.
  7. Barenius B, Ponzer S, Shalabi A, Bujak R, Norlen L, Eriksson K. Increased Risk of Osteoarthritis After Anterior Cruciate Ligament Reconstruction: A 14-Year Follow-up Study of a Randomized Controlled Trial. Am J Sports Med. 2014;42(5):1049-1057. doi:10.1177/0363546514526139.
  8. Luc B, Gribble PA, Pietrosimone BG. Osteoarthritis prevalence following anterior cruciate ligament reconstruction: a systematic review and numbers-needed-to-treat analysis. J Athl Train. 2013;49(6):806-819. doi:10.4085/1062-6050-49.3.35.
  9. Grimm NL, Jacobs Jr. JC, Kim J, Denney BS, Shea KG. Anterior Cruciate Ligament and Knee Injury Prevention Programs for Soccer Players: A Systematic Review and Meta-analysis. Am J Sport Med. 2014. doi:10.1177/0363546514556737.
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