Anterior Cruciate Ligament (ACL) Injury: Prevalence in Sports Rehabilitation
By Tyler Meyers PT, DPT
Prevalence in Sport and Gender
Between the sex of the patient and the sport performed, the risk for ACL injuries will vary. A study performed by Children’s Hospital of Philadelphia1 analyzed the risk of ACL injury based on sport and sex. The highest risk of injury for females is associated with basketball and soccer while the highest risk of injury for males is associated with football. Across the table it is seen that with the sports performed by both sexes, females have an inherently higher risk of injury. With most males and females participating in more than one sport throughout the year this table can give a cumulative risk of injury for the year. The examples given showed that if a male plays one season of basketball, football, and baseball they have about a 1% risk of tearing their ACL over the course of a single school year. For a female, if they were to specialize in soccer and play it for all four seasons, they would have a 4.4% risk of tearing their ACL over the course of a single school year.
Predisposition for Females to Injury
There are anatomical and biomechanical factors that predispose females to a greater risk of ACL injury than males.2,3,4 First, females have a wider pelvis creating a greater Q angle. The wider pelvis of a female causes the femur to have a greater angle towards the knee. Muscle strength is greatly impacted by a length-tension relationship which is negatively impacted by the greater Q angle. With decreased muscle strength, this means that the knee now has less dynamic support than is required for sport performance. The second major factor is that as younger females physically develop, they experience hormonal changes that can affect the laxity of ligaments. Increased laxity within the ligament will allow for greater translation with different sport movements causing increased stress on the ligament. The ligament laxity can also lead to increased risk of recurrent injury following an ACL reconstruction. The variation in female anatomy leads to deficit in movement, alignment, and strength which decreases their ability to absorb the forces associated with jumping, landing, cutting, and deceleration. During practice and competition, the aspect of fatigue will begin to magnify all of the factors noted above. Fatigue will decrease the hamstrings and quadriceps ability to absorb forces placing more on the ACL with a dynamic knee valgus position, especially with the landing phase of a jump.
Taking these factors into consideration the focus must shift toward the prevention of these injuries to help decrease the female’s inherent risk. Decreasing the forces placed on the ACL in a dynamic knee valgus position that is commonly seen in females when jumping, landing, cutting, and decelerating is of upmost priority in injury prevention. The Journal of Sports Physical Therapy introduced a knee injury prevention clinical practice guideline to help address the increased risk factors. The warm-up routine is divided into three components: dynamic warm-up, foundational strengthening, and movement coordination, deceleration, cutting, and plyometric training. A video detailing the warm-up exercise sequence can be found here.5
References
1. Beck NA, Lawrence TR, Nordin JD, et al. ACL tears in school-aged children and adolescents over 20 years. J Pediatr. 2017;139(3)
2. Parsons JL, Coen SE, Bekker S. Anterior cruciate ligament injury: towards a gendered environmental approach. Br J Sports Med. 2021;55(17):984-990
3. McLean SG, Huang X, Van Den Bogert AJ. Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: implications for ACL injury. Clin Biomech. 2005;20(8):863-870
4. Mountcastle SB, Posner M, Kragh JF, et al. Gender differences in anterior cruciate ligament injury vary with activity: epidemiology of anterior cruciate ligament injuries in a young, athletic population. Am J Sports Med. 2007; 35(10): 1635-1642
5. Knee injury prevention CPG: warm up exercise sequence for field sports. Available from: https://www.youtube.com/watch?v=RfROpda4kvg