Anterior Cruciate Ligament Injuries in Female Soccer Players

Introduction

Since the passing of Title IX in 1972, female participation in sports at every level has increased tremendously and continues to grow. ^, With that, however, the prevalence of sports-related musculoskeletal injuries has also greatly increased in the female athlete. In particular, anterior cruciate ligament (ACL) injuries have become a critical issue for a variety of reasons, including the severity of the injury itself; time loss from participation in sports, recovery, and rehabilitation from surgery; and long-term consequences of injury, such as osteoarthritis. In addition to the substantial impacts an ACL injury has on an individual, the healthcare costs of reconstruction surgery and postoperative rehabilitation, as well as costs associated with nonsurgical treatment, are extremely high, surpassing $100 million per year. Female soccer players especially are a high-risk population, and among all athletes in general, they are some of the most frequent to be affected by ACL injuries. Female soccer players are at a significantly greater risk of sustaining a sprain or tear to the ligament compared with other female athletes participating in a variety of other sports, and even more so when compared with male soccer players.

The ACL functions as a knee stabilizer by preventing anterior translation of the tibia and providing rotational stability. The knee support provided by the ACL is key for multidirectional cutting, landing, and pivoting sports such as soccer. With a functional deficit of the ACL, performing these actions are challenging and it risks further injury, resulting in many ACL-injured athletes to be unable to return to their preinjury level of play, or even to quit playing. After reconstruction, athletes remain at high risk for reinjury of the index knee and for injury of the contralateral ACL, and female soccer players have been reported to be among athletes with the highest risk for these occurrences. Awareness of the prevalence and the severity of multiple factors related to ACL injury among female soccer players is an important step toward implementing prevention techniques to ultimately decrease the incidence of injury. Additionally, a better understanding of the mechanisms and multifaceted risk factors that cause this injury, as well as awareness of the additional risks and frequency of graft failure and second ACL injuries, are valuable information for proper treatment. Finally, knowledge of the efficacy of current prevention programs that exist and placing high importance on the need for intervention can provide athletes, coaches, trainers, and parents with methods in which they can minimize the risk of ACL injury.

Epidemiology

With increasing awareness of the severity of ACL injury in the athletic population, many epidemiology studies have been conducted on high-risk populations, such as female soccer players, particularly highlighting the difference in injury rates between males and females. In 2005, Agel et al. reported the ACL injury rate for basketball and soccer at the collegiate level in a 13-year review. Overall, there was a total of 1268 ACL injuries with 586 sustained while playing soccer, and within soccer, there were 394 ACL injuries in females versus 194 in males. It was also observed that soccer players sustained consistently more ACL injuries than basketball players. Throughout the study, the incidence of ACL injury in males reduced, whereas the rate in females remained constant, widening the magnitude of the disparity of injury rate between males and females. In an updated review of ACL injury rates across 15 different sports at the collegiate level over a 9-year period, Agel et al. observed a similar trend within soccer that female athletes sustained significantly more ACL injuries than male athletes at over double the rate. Overall, 71 females and 26 males experienced an ACL injury, signified by rates of 0.10 versus 0.04 per 1000 athletic exposures (AEs), respectively. Interestingly, there was a significant increase in injury rate per year over the course of this study, but these results also represented a 64% decrease in overall ACL injury rate in females and 56% decrease in males compared to the researchers' original data from their previous study.

To further emphasize the consistency of the epidemiology of ACL injuries in female soccer players, a review published in 1995 found a higher prevalence of knee injuries in female soccer players than in males over the course of the 5-year study period, despite the fact that there were significantly more men's teams included in the study (461 men's teams vs. 278 women's teams). The ACL injury rate was over double in the female athletes (0.31 vs. 0.13 per 1000 AEs) and 68% of females who sustained an ACL injury required surgery versus 59% of males. Notably, females also had a consistently higher rate of injury in any given year throughout the study period by at least double compared to males, in addition to a higher overall average rate.

Prodromos et al. also noted that the rate of ACL injury was three times higher in female soccer players than in male soccer players (5% vs. 1.7%, respectively) participating in year-round high-level competition. Hootman et al., who studied the epidemiology of all injuries at the collegiate level over a 16-year study period, reported that soccer players sustained 579 of the 4800 ACL injuries among 15 sports. Within soccer, 411 of the ACL injuries occurred in females, whereas just 168 were suffered by males, represented by a difference in injury rate of 0.28 versus 0.09 per 1000 AEs, respectively. At the high-school level, Joseph et al. also performed a multisport epidemiology study specifically comparing ACL injury patterns. The greatest prevalence of ACL injury was found in female soccer players, at a rate of 12.2 per 100,000 AEs, and among all the female athletes included in the study, 53.2% of ACL injuries occurred in soccer players. Overall, girls were twice as likely to sustain an ACL injury playing soccer compared to any other sport included in this population of high-school athletes. In a study, Larruskain et al. prospectively compared injuries between male and female elite soccer players over the course of eight seasons. A total of 50 males and 35 females participated and they all belonged to the same club and had the same medical staff. At this high level of play, ACL ruptures were 5 times more common in females, which resulted in over 40% of the absences from play that female athletes experienced. Females had a 21% greater amount of total days lost from participation, representing an injury burden twice as high compared to males, as well as a higher proportion of severe injuries overall.

When observing the incidence of ACL injuries in female soccer players compared to the risk of other injury types, ACL ruptures may always account for the majority, but they are still considered to be among the most severe type of injury with a high injury burden. ^{, ,} Faude et al. prospectively analyzed injury incidences in female soccer players in the German National League over the course of a single season. A total of 165 players were included in the study, and on average, each player participated in 183 h of training and spent 31 h in matches. Overall, 241 injuries were sustained by 115 players (70% of the athletes) and 58% of the total injuries were severe injuries of the knee. Among them were 11 ACL ruptures sustained by 10 players (6% of all athletes), resulting in an incidence rate of 2.2 per 1000 match-hours. The average time lost from participation because of ACL injury was half of the year (178 days), which the authors noted that the severity of this injury and the high amount of time lost comes at a great disadvantage to the team and cost for the club. Not only is the team impacted but also the consequences for the athlete include risks of permanent disability of the injured knee, emphasizing the importance of finding effective prevention methods. Giza et al. also reported injuries in professional female soccer players and found that ACL injuries consisted of 4.6% of all injuries (8 of 173) and 14.6% of all knee injuries (8 of 55), and the incidence of ACL tears was 0.09 per 1000 player-hours. Le Gall et al. studied the incidence of injuries in young elite female soccer players prospectively over eight seasons, and out of the 119 players that participated in this study, 110 (92.4% of the athletes) experienced a total of 619 injuries. A majority of the injuries occurred in the youngest team (Under-15) and the least amount of injuries occurred in the oldest team (Under-19). Of the 619 injuries, a total of 12 ACL injuries were sustained by 11 players, with 7 of them occurring in the nondominant leg. Interestingly, no ACL injuries were reported in the last 3 years of the study, which the authors attributed to the introduction of a prophylactic conditioning program. Despite this, it was noted that the overall risk of ACL injury was comparable to adult elite female soccer players, which confirms the ongoing importance for intervention in the entire population of female soccer athletes and a further understanding of the many aspects associated with this specific injury.

Mechanisms and Risk Factors