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Ten-Year Epidemiology of Ankle Injuries in Men's and Women's Collegiate Soccer Players.

CONTEXT
Data from the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP) has indicated that ankle injuries are the most common injuries among NCAA soccer players.


OBJECTIVE
To review 10 years of NCAA-ISP data for soccer players' ankle injuries to understand how the time period (2004-2005 through 2008-2009 versus 2009-2010 through 2013-2014), anatomical structure injured, and sex of the athlete affected the injury rate, mechanism, and prognoses.


DESIGN
Descriptive epidemiology study.


SETTING
Online injury surveillance.


MAIN OUTCOME MEASURE(S)
The NCAA-ISP was queried for men's and women's soccer ankle data from 2004 to 2014. Ankle injury rates were calculated on the basis of injuries per 1000 athlete-exposures. Rate ratios (RRs) were used to compare injury rates. Injury proportion ratios (IPRs) were used to compare injury characteristics.


RESULTS
When compared with the 2004-2005 through 2008-2009 seasons, the 2009-2010 through 2013-2014 seasons showed a similar rate of injuries (RR = 0.94, 95% confidence interval [CI] = 0.85, 1.04) but fewer days missed (P < .001) and fewer recurrent injuries (IPR = 0.55, 95% CI = 0.41, 0.74). The 4 most common ankle injuries, which accounted for 95% of ankle injuries, were lateral ligament complex tears (65.67%), tibiofibular ligament (high ankle) sprains (10.3%), contusions (10.1%), and medial (deltoid) ligament tears (9.77%). Of these injuries, high ankle sprains were most likely to cause athletes to miss ≥30+ days (IPR = 1.9, 95% CI = 1.24, 2.90). Men and women had similar injury rates (RR = 1.02, 95% CI = 0.94, 1.11). Men had more contact injuries (IPR = 1.28, 95% CI = 1.16, 1.41) and contusion injuries (IPR = 1.34, CI = 1.03, 1.73) but fewer noncontact injuries (IPR = 0.86, 95% CI = 0.78, 0.95) and lateral ligamentous complex injuries (IPR = 0.92, 95% CI = 0.86, 0.98).


CONCLUSIONS
Although the rate of ankle injuries did not change between the 2004-2005 through 2008-2009 seasons and the 2009-2010 through 2013-2014 seasons, the prognoses improved. Among the 4 most common ankle injuries, high ankle sprains resulted in the worst prognosis. Overall, male and female NCAA soccer players injured their ankles at similar rates; however, men were more likely to sustain contact injuries.

An AE is defined as 1 athletic event for each athlete. For example, if 1 practice consists of 20 participating players, 20 AEs are counted. Among injuries to NCAA soccer players, the ankle is the most common site of injury, accounting for 17% of all injuries among this population. [3][4][5][6] Among NCAA sports, only basketball resulted in higher rates of ankle injury than soccer. 7 The high rate of ankle injuries among soccer players is due to the frequent changes of directions and jumping while wearing cleated shoes with little ankle support. 7 These injuries often result in pain, instability, diminished performance, absence from competition, and psychological stress, 3,4,6-8 which make accurate diagnosis, treatment, and injury prevention paramount.
Due to the large number of injuries, the NCAA and athletic trainers (ATs) constantly work to identify methods of making collegiate sports safer. The NCAA modifies rules to restrict the number of preseason practices, games, and hours per week a team can practice. It also implements rules regarding the types of contact allowed during games and the equipment that players must use during games. One prominent example of this in NCAA soccer is the mandate for shin guards to be worn during all games. Since being implemented, this rule has been changed to include specific requirements regarding the size and location of the shin guards. 3 Also, ATs have worked to improve braces, taping techniques, and modes of rehabilitation, including the increased use of proprioceptive training, to protect athletes. 2,[9][10][11] Because of these changes, it is important to compare types, mechanisms, and trends of ankle injuries between time periods to determine whether the interventions have been effective.
One important job of ATs and team physicians is recognizing and differentiating the common types of injuries among athletes. Although it is widely reported that most NCAA soccer injuries affect the ankle, fewer data differentiating the specific types of ankle injuries have been available. 3,4,6 The 4 most common ankle injuries among soccer players were lateral ligament complex (LLC) sprains, tibiofibular (high ankle) sprains, medial (deltoid) ligament sprains, and ankle contusions. 3,4,7,12,13 The LLC sprains were the most frequent of all ankle injuries, whereas high ankle sprains resulted in the worst prognosis. 7,12,[13][14][15] Expanding the available data regarding specific types of injuries will help facilitate future approaches to prevention, treatment, and prognosis.
Another important aspect guiding the efforts of ATs and team physicians is understanding the role that sex plays in the types, rates, and mechanisms of ankle injuries. Discrepancies such as joint laxity, hormones, height, weight, strength, mechanical axis, and levels of contact may contribute to differences in the ankle injuries of male and female athletes. 2,4,8,16 Previous researchers addressed only how sex affected the rate of ankle injury, with no mention of how it might have affected the type or mechanism of ankle injury. Also, the results 3,4,8,16 have been inconsistent, with studies suggesting similar rates in both sexes, increased rates in men, or increased rates in women. Understanding the effect of a player's sex on ankle injuries can help guide future decisions for sex-specific taping techniques, braces, shin-guard rules, preventive muscular strengthening, and treatment.
The purpose of our study was to review 10 years of NCAA soccer players' ankle injuries and identify the differences among the various anatomical structures injured, between men and women, and between the  IN), an independent, nonprofit research organization, received data from NCAA soccer ATs and physicians, analyzed them, and reviewed them to ensure quality.

Data Collection
We briefly describe the inclusion criteria and methods of the NCAA-ISP as they pertain to this research, but more detailed information can be found in ''National Collegiate Athletic Association Injury Surveillance System: Review of Methods for 2004-2005 Through 2013-2014 Data Collection.'' 17 Athletic trainers reported injury data during organized practices and games from the participating NCAA sports programs. Each game or practice counted as 1 AE. During the 2004-2005 through 2008-2009 seasons, ATs used written questionnaires that they faxed or mailed to the NCAA. During the 2009-2010 through 2013-2014 seasons, ATs used electronic medical records to collect and organize the data. They could return and add or change data throughout the season as they saw fit. Common data elements were deidentified, collected, and added to a central aggregate research database. Data sent to the database were verified, evaluated for consistency, and flagged when invalid values were recorded. The ATs and quality-assurance staff worked together to resolve any concerns about data validity. Consistent and usable data were then added to the aggregate research database.
An AE was reported as 1 student-athlete participating in 1 NCAA-sanctioned practice or game. Injuries that were reported included those that occurred during a teamsanctioned practice or game and were evaluated by an AT or physician. The structure injured was determined via evaluation by an AT or team physician, with or without the aid of magnetic resonance imaging.

Statistical Analysis
We analyzed injury rates using number of injuries per 1000 AEs; t tests were conducted to compare means, rate ratios (RRs) to compare injury rates, and injury proportion ratios

Other Notable Results
Ankle injuries occurred at a rate of 3.05 per 1000 AEs during games and 0.93 per 1000 AEs during practices. When compared with practices, games resulted in an ankleinjury RR of 3.33 (95% CI ¼ 3.05, 3.63). New injuries constituted 84.3% (n ¼ 1767) of total ankle injuries, whereas 15.7% (n ¼ 328) were recurrent.
For every 1000 AEs, injuries occurred at a rate of 1.30 during the preseason, 1.51 during the season, and 0.95   , anatomical structure injured, and sex of the athlete affected the injury rate, mechanism, and prognosis.

Overall Results
These findings correlate with those of many other investigators 3,4,7,12,18 who found that ankle injuries during games occurred at a rate 3 times greater than during practices (RR ¼ 3.33; 95% CI ¼ 3.05, 3.63). Furthermore, these results align with data from other studies 19,20 suggesting that injuries occurred more often during the second half of soccer games than during the first half (RR ¼ 1.32; 95% CI ¼ 1.20, 1.44). The increased injury rate during the second half could be attributed to athlete fatigue. [19][20][21] Regarding the time of year in which injuries occurred, soccer players were more likely to be injured during preseason practices than during regular season practices (RR ¼ 1.57; 95% CI ¼ 1.39, 1.79). This value is consistent with the results of other authors 3,4,7 and could indicate that players beginning the preseason are less conditioned and, therefore, more likely to be injured.
Fortunately, when ankle injuries occur in these athletes, they often result in only a brief period of time being missed. In fact, many soccer players returned to the event in which they sustained the ankle injury. 7,9 Furthermore, of the 1982 injuries for which we have a record of days lost, 58.93% (n ¼ 1168) resulted in 0 to 6 days missed, and only 5.65% (n ¼ 112) resulted in 30 days missed. However, the time lost varied significantly depending on the anatomical structure injured.

Injured Anatomical Structure
Of the 4 most common ankle injuries, contusions resulted in the smallest number of days missed (males ¼ 4.33 days, females ¼ 6.58 days) and high ankle sprains resulted in the most days missed (males ¼ 12.86, females ¼ 16.97; Table  3). Lateral ligamentous complex tears and medial (deltoid) tears were associated with similar numbers of days missed after injury (Table 3). Among the 4 frequent ankle injuries, high ankle sprains had the worst prognosis. 14,15 In our study, when compared with the other 3 common ankle injuries, high ankle sprains were most likely to cause an athlete to miss 30 days (IPR ¼ 1.90; 95% CI ¼ 1.24, 2.90). Also, only 37.9% (n ¼ 78) of athletes who had a high ankle sprain returned within a week of injury. High ankle sprains a P values showed no difference between sexes. are usually caused by eversion or external rotation (or both). 14,15 The prolonged period of pain and instability from these injuries can be attributed to the anterior tibiofibular ligament, which is typically injured during high ankle sprains. This ligament is a syndesmosis that keeps the tibia and fibula connected and functioning in unison. 14,15 As an athlete runs and cuts, large forces traverse the tibia and fibula, applying significant stress to the relatively small anterior tibiofibular ligament. 14,15 These large forces cause lingering periods of pain and instability after high ankle sprains. 14,15 Similar to the current literature, 3,4,7 we found that the LLC was the most commonly injured anatomical structure, accounting for 65.67% (n ¼ 1358) of ankle injuries. The mechanism of LLC injuries is inversion of the ankle joint. 7,14,18 Structurally, the fibula, which lies on the lateral aspect of the ankle, extends farther distally than the tibia, allowing the ankle to invert more readily than evert. 9 This relatively easy inversion allows athletes to ''roll'' the ankle in supination, often resulting in an LLC tear. 9 The LLC includes the anterior talofibular, calcaneofibular, and posterior talofibular ligaments. 7 The anterior talofibular    Table 5. The 95% confidence intervals shown in Table 5 suggest differences in the injury proportion ratios (IPRs) at each ''Days Missed due to Injury'' interval.
ligament is the weakest of the LLC ligaments and, therefore, the most likely to be injured during inversion. 9,14 Also, the anterior talofibular is the primary lateral ligament stressed in plantar flexion and inversion, which occurs when the ankle is in its most vulnerable position due to the narrower geometry of the posterior talus. 9,14 Although some LLC tears resulted from contact with another player, they were more likely to occur without contact (Table 7). This could be due to hyperinversion, as when an athlete landed from a jump, cut, or stepped on uneven ground. 9,14 Conversely, medial ligament ankle tears were more likely to be due to contact with another player (Table 7). This can be explained, once again, by the relative length of the fibula compared with the tibia. 9 Because the fibula extends farther than the tibia, hypereversion of the ankle is more difficult and more likely to require an external force, such as contact with another player.
Lateral ligament complex tears, deltoid tears, contusions, and high ankle sprains were more frequent during games than during practices, but contusions showed the highest RR during games (Table 6). This is probably because contusions were more likely to result from contact than noncontact ( Table 7). Given that games are often associated with greater intensity than practices, games may also lead to increased contact, thereby causing a higher incidence of contact injuries. 3,4 When we categorized the 4 most common ankle injuries as new or recurrent, all were typically described as new (Table 8). However, it is important to recognize that these data may be inaccurate because ATs and team physicians do not always know an athlete's medical history and may incorrectly classify a recurrent injury as new. Still, advances in physical therapy, strengthening exercises, taping, and bracing probably contributed to the lower number of recurrent injuries.

Males Versus Females
For males and females, the injury rates (Table 1) and the time to return to activity after ankle injury (Table 2) were similar. Yet males were more likely to be injured by contact with another player (IPR ¼ 1.28; 95% CI ¼ 1.16, 1.41) and while being slide tackled (IPR ¼ 1.90; CI ¼ 1.30, 2.78) and less likely to incur a noncontact ankle injury (IPR ¼ 0.86; CI ¼ 0.78, 0.95) or an injury due to contact with an apparatus (IPR ¼ 0.57; 95% CI ¼ 0.43, 0.76). Also, males were more likely to be injured during games (RR ¼ 1.14; 95% CI ¼ 1.01, 1.29) and to sustain contusions (IPR ¼ 1.34; 95% CI ¼ 1.03, 1.73). The similar rates of ankle injuries among NCAA soccer players have been well described in the literature. 3,4 The increase in game injuries, contact injuries, and contusion injuries may be due to the increased contact in men's sports compared with women's sports. 22,23 In comparing the anatomical structure injured, males and females showed similar IPRs for high ankle sprains and medial (deltoid) tears (Table 2), but males were less likely to experience an LLC tear (IPR ¼ 0.92; 95% CI ¼ 0.86, 0.98). The slight increase in LLC tears among females could result from the increased LLC laxity that has been described previously. 22,23 Prior authors 2,4,8,16 showed discrepancies in joint laxity, hormones, height, weight, strength, mechanical axis, and level of contact among males and females that may contribute to ankle injuries. Recognizing the differences in injuries between sexes may lead to the creation of and changes in sex-specific rule revisions and ankle exercises.   , .001). Decreases in the number of recurrent ankle injuries and the days lost per injury may reflect continuing advances in rehabilitation and injury prevention. 6,10,19,24 Athletes were able to return to soccer more quickly in the most recent time period, perhaps because ATs and team physicians prescribed early proprioceptive training and earlier use of physical therapy as opposed to immobilization, which was commonly prescribed in the past. 6,10,19,24 It is interesting that even though athletes were returning to play more quickly, they sustained fewer recurrent injuries.
Advances in prevention such as taping, bracing, and injuryspecific weight-training regimens may be responsible. 6,10,19,24 Previous researchers 2 showed similar decreases in injury severity and recurrence  (Table 4). One possibility for this decrease is that coaches, ATs, and team physicians were more aware of the increased preseason injury rates and attempted to decrease the intensity and full-contact periods during preseason practices. Another potential reason for this decrease is the use of off-season strength and conditioning programs to help the athletes begin preseason workouts in better condition. Another effort to protect athletes addressed by the NCAA was the update and implementation of rules regarding shin guards, which were first mandated for NCAA soccer players in 1991. 3 Since then, the size and use of shin guards have undergone changes. 3 The most current update 3 regarding shin-guard rules (established in 2007) stated that they must ''meet the standards established by the National Operating Committee on Standards for Athletic Equipment (NOC-SAE).'' Shin guards prevent contusions and fractures. Because of the small number of fractures among NCAA soccer players (n ¼ 9), these injuries were not included in our study. However, shin guards have failed to decrease the number of contusions. In fact, the proportion of contusions

LIMITATIONS
Previous investigators 26 determined that in the years 2005-2007, of the programs that provided data to the NCAA-ISP, 88.5% of NCAA soccer injuries were reported. Thus, the data we used in this study represent a majority but not all of the injuries that occurred during these seasons. Our data only accounted for injuries reported by ATs and medical staff. It is possible that injuries were reported incorrectly; for example, a new AT who had not previously worked with a particular athlete could have marked an injury as new when it was actually recurrent. The immobility and rehabilitation measures used for recovery in these athletes were not described, and time-out-of-play data did not control for these extenuating variables. Also, LLC tears, medial (deltoid) ligament tears, and high ankle sprains were not differentiated as partial or complete. Another inherent limitation of the data used in this study was that the diagnoses were made by many different ATs and physicians, and we do not know whether physical examinations or magnetic resonance imaging were undertaken.
Many However, the 2004-2009 seasons did not include injuries that resulted in no time loss. Therefore, when comparing average days lost between these time periods, the analysis may be biased.

CONCLUSIONS
Although the rate of ankle injuries did not change between the 2004-2005 through 2008-2009 and 2009-2010 through 2013-2014 seasons, the prognoses improved. Of the 4 most common ankle injuries, high ankle sprains resulted in the worst prognosis. Overall, male and female NCAA soccer players injured their ankles at similar rates; however, males were more likely to have contact injuries.