Anterior Cruciate Ligament (ACL) tears are by no means an injury foreign to athletes and the medical personnel who work with them, and they’re perhaps more common than you think: 1 in 3500 people in the United States report an ACL tear every year ! This frequency makes it even more crucial for medical officers to understand the risk factors that predispose someone to an ACL injury. We have an article that focuses on the risk factors in athletes particularly. However, here, we evaluate the musculoskeletal and genetic risk factors that medical officers can identify when screening patients to ensure that their patients have a better chance of preventing potential ACL tears.
In a review of the extant literature on ACL injuries, Pfeifer and colleagues (2018) remark on the clear distinction between extrinsic and intrinsic factors that can increase susceptibility to ACL injuries . Whilst extrinsic factors are those outside the patient’s control that have to do with the sport and physical surroundings, intrinsic factors include anatomical, neuromuscular, biomechanical, physiologic, and genetic influences. Intrinsic risk factors are further classified as modifiable (something the patient can change like flexibility or muscle strength) or non-modifiable (something the patient cannot change like musculoskeletal and genetic factors).
In this review published in the International Journal of Sports Physical Therapy, these researchers discovered a common consensus of intrinsic musculoskeletal factors that increase the likelihood of an ACL injury . Anatomical factors, such as having a narrow intercondylar notch and an increased posterior or lateral tibial slope, increased one’s susceptibility to ACL injury. Specifically in female athletes, neuromuscular factors like decreased muscular strength of muscles of the hamstrings, core and trunk, hip abductors and external rotators increased their risk of injury. Additionally, musculoskeletal factors like increased knee abduction angles, decreased knee flexion angles, increased general joint laxity, decreased H/Q ratios and femoral intercondylar notch width have also been termed risk factors as a result of kinesiology research that studied prescreened female twins presenting these conditions that subsequently sustained ACL tears .
Part 2 of a research study by Smith and colleagues (2012) indicates that patients with an ACL injury are more likely to have a family member with an ACL injury as well . Furthermore, if there is a history of ACL injuries in the family, there is a genetic component that predisposes other relatives to sustaining them. Bram et al. (2020) conducted a mini review of studies that have investigated this that found that the percentages of patients with ACL tears who also had first degree family members with ACL tears were anywhere between 16% and 38% . During this study, these researchers distributed a questionnaire to 450 pediatric patients who had sustained ACL injuries and found that 25% of their respondents had at least one family member with the same injury.
Additionally, there has also been some investigation regarding which genes in particular provide this predisposition. Variants of the collagen genes or proteoglycan genes have been implicated in the predisposition of individuals of both sexes to ACL tears . It is to be noted, however, that the study conducted on the variants of the collagen genes were based on unmatched case-controls and a white South African population. While this limits the generalizability of the results and calls for further research on a more diverse population, it suggests that the collagen gene is one to keep in mind. Similarly, the conclusions of the genetic studies in this area of research must be drawn sparingly as several sources of bias have been identified . More research on ethnically and racially diverse populations is needed before generalizations about genetic expressions can be made.
Because of non-modifiable intrinsic risk factors, like the musculoskeletal and genetic factors discussed above, there is always a chance of at-risk patients sustaining an ACL injury . However, acknowledging these factors should give both medical officers confidence in recommending prevention plans for their patients and give their patients more awareness in preventing future ACL injury.
- Evans, J., & Nielson, J. I. (2021). Anterior Cruciate Ligament Knee Injuries. NCBI. StatPearls Publishing LLC. https://www.ncbi.nlm.nih.gov/books/NBK499848/.
- Pfeifer, C. E., Beattie, P. F., Sacko, R. S., & Hand, A. (2018). RISK FACTORS ASSOCIATED WITH NON-CONTACT ANTERIOR CRUCIATE LIGAMENT INJURY: A SYSTEMATIC REVIEW. International Journal of Sports Physical Therapy, 13(4), 575–587. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6088120/
- Hewett, T. E., Lynch, T. R., Myer, G. D., Ford, K. R., Gwin, R. C., & Heidt, R. S. (2009). Multiple risk factors related to familial predisposition to anterior cruciate ligament injury: fraternal twin sisters with anterior cruciate ligament ruptures. British Journal of Sports Medicine, 44(12), 848–855. https://doi.org/10.1136/bjsm.2008.055798
- Smith, H. C., Vacek, P., Johnson, R. J., Slauterbeck, J. R., Hashemi, J., Shultz, S., &; Beynnon, B. D. (2012). Risk Factors for Anterior Cruciate Ligament Injury: A Review of the Literature—Part 2: Hormonal, Genetic, Cognitive Function, Previous Injury, and Extrinsic Risk Factors. Sports Health: A Multidisciplinary Approach, 4(2), 155–161. https://doi.org/10.1177/1941738111428282
- Bram, J. T., Pascual-Leone, N., Patel, N. M., DeFrancesco, C. J., Talathi, N. S., &; Ganley, T. J. (2020). Do Pediatric Patients With Anterior Cruciate Ligament Tears Have a Higher Rate of Familial Anterior Cruciate Ligament Injury? Orthopaedic Journal of Sports Medicine, 8(10), 232596712095966. https://doi.org/10.1177/2325967120959665
- John, R., Dhillon, M. S., Sharma, S., Prabhakar, S., &; Bhandari, M. (2016). Is There a Genetic Predisposition to Anterior Cruciate Ligament Tear? A Systematic Review. The American Journal of Sports Medicine, 44(12), 3262–3269. https://doi.org/10.1177/0363546515624467