My Daughter Is a High School Basketball Athlete. What Are the Risks of Tearing Her ACL? If She Has That Knee Fixed, What Are the Risks for the Opposite Knee? Are There ACL Injury Prevention Programs Available?
Anterior cruciate ligament (ACL) injury occurs with a 4-fold to 6-fold greater incidence in female athletes compared to male athletes playing the same cutting and landing sports.1 Injury rates vary according to sex, sport played, and level of participation. There have been several studies that have examined differences between genders that may account for an increased incidence of ACL tears in women. In part, this research has lead to successful training programs that aim to decrease the number of ACL tears in female athletes.
For females playing high school basketball, the overall injury rate per 100 players is 28.7, with 15.7% of these injuries occurring in the knee (4.5 injuries per 100 players).2 Rebounding in practice is the most frequently reported activity during injury. A recent study suggests that patients who rupture their ACL have a 6.4% chance of rerupturing their reconstructed ACL graft and a 5.7% chance of rupturing the ACL on their opposite knee within 5 years. In other words, the risk of suffering an ACL tear to either the reconstructed knee or the contralateral knee is nearly identical.3 Other authors have shown that athletes returning to sports that specifically involve cutting and pivoting are more likely to rupture their contralateral ACL rather than their reconstructed ACL.3,4
Why do female athletes have a higher incidence of ACL tears than males? The mechanism underlying the gender disparity is likely multifactorial. Several theories have been proposed, and they include anatomical, hormonal, and neuromuscular differences between genders.
Numerous anatomic distinctions have been observed between male and female athletes. The differences include the presence of the following in females: a wider pelvis, increased Q angle, smaller notch width, smaller ACL, increased generalized joint laxity, increased hamstring flexibility, increased anterior tibial translation, and increased foot pronation/navicular drop.5 However, no one anatomical risk factor has been directly and independently correlated to an increase in noncontact ACL injury.
Numerous studies have examined the effect of hormones on ACL tears. It has been shown that estrogen can affect the tensile properties of ligaments and estrogen receptors are present in female ACL fibroblasts. Moreover, estrogen has been shown to alter neuromuscular function in both the central and peripheral nervous system.5 As with the anatomical differences between sexes, it seems that the literature has an equal number of researchers who agree and disagree as to the effect of hormones on the incidence of ACL tears.
More recently, neuromuscular differences between men and women have been examined in order to explain the difference in the incidence of ACL tears. Wojtys demonstrated that women exhibit less muscular protection of the knee ligaments with the tibia in internal rotation than men.6 Perhaps the most important finding to date is the precision with which males and females are able to decelerate from landing and control dynamic valgus and tibial translation. This is thought to be the result of a discrepancy in the balance between hamstring-to-quadriceps strength and recruitment. Thus, when a female lands from a jump she is more prone to hyperextend her knee and suffer a noncontact ACL injury.
The latest research on neuromuscular control and the differences that exist between men and women have led to programs aimed at ACL injury prevention. Neuromuscular and proprioceptive training in female athletes has been shown to increase active knee stabilization in the laboratory and decrease the incidence of ACL injury.7 There are a number of successful training programs that teach female athletes how to actively recruit muscles that decrease joint motion and protect the ACL during athletic activity, primarily landing from a jump. A recent study by Mandelbaum showed that a neuromuscular and proprioceptive training program was effective in decreasing the number of ACL tears in women by an average of 81% over a period of 2 years.8
There are many programs whose goals are to prevent injury to the ACL. The program described by Mandelbaum, PEP (Prevent Injury and Enhance Performance), shares numerous similarities with other preventative programs.8 Athletes watch a videotape and are instructed to perform several stretching and strengthening exercises for their trunk and lower extremity as well as a number of plyometric and agility drills during their routine warm-up. Most importantly, this program emphasizes proper cutting and landing techniques. This includes engaging hip and knee flexion, avoiding genu valgum at the knee on landing and lateral maneuvers, and addressing proper deceleration techniques. The program also employs strengthening the hip abductors and hamstrings.
The incidence of injury to the ACL is currently more common in women than men. There are many anatomical, hormonal, and neuromuscular differences between the 2 sexes that may account for this discrepancy. However, with continuing research and more attention to programs that promote neuromuscular and proprioceptive training, we may begin to see fewer ACL tears in the female athlete.
1. Arendt E, Dick R. Knee injury patterns among men and women in collegiate basketball and soccer: NCAA data and review of literature. Am J Sports Med. 1995;23:694-701.
2. Powell JW, Kim D, Barber-Foss. Sex-related injury patterns among selected high school sports. Am J Sports Med. 2000;28:385-391.
3. Salmon LB, Russell VB, Musgrove TM, et al. Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction. Arthroscopy. 2005;21(8):948-957.
4. Shelbourne K, Davis T, Klootwyk T. The relationship between intercondylar notch width of the femur and the incidence of anterior cruciate ligament tears. Am J Sports Med. 1998;26:402-408.
5. Hewett TE, Myer GD, Ford KR. Anterior cruciate ligament injuries in female athletes: part 1, mechanisms and risk factors. Am J Sports Med. 2006;34:299-311.
6. Wojtys EM, Huston LJ, Schock HJ, Boylan JP, Ashton-Miller JA. Gender differences in muscular protection of the knee in torsion in size-matched athletes. J Bone Joint Surg Am. 2003;85:782-789.
7. Hewett TE, Lindenfeld TN, Riccobene JV, Noyes FR. The effect of neuromuscular training on the incidence of knee injury in female athletes: a prospective study. Am J Sports Med. 1999;27:699-706.
8. Mandelbaum BR, Silvers HJ, Watanabe JF, et al. Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female athletes: 2-year follow-up. Am J Sports Med. 2005;33:1103-1010.