August 2013

Digging in to prevent ACL injuries in volleyball

shutterstock_83258800_croppedLanding and change of direction in volleyball can put players at risk of anterior cruciate ligament (ACL) injury. Few ACL prevention studies have focused on volleyball, but players can benefit from screening and intervention programs that have been shown to be effective in other sports.

By Joanne L. Parsons, MSc, PT, CAT(C)

Injury to the anterior cruciate ligament (ACL) of the knee is a devastating event that can remove an athlete from play for months; in fact, many athletes never return to their original level of competition.1 Athletes, parents, and coaches involved in the sport of volleyball are aware the injury can cause significant joint instability, pain, and altered function.

Less recognized is that ACL injury may also lead to development of osteoarthritis in the affected joint, especially if other ligamentous or meniscal damage occurs at the time of injury.2 Therefore, it is important for those involved in volleyball to understand the likelihood of injury, the mechanisms that can lead to injury, and what strategies can be put in place to decrease the possibility of injury occurrence.

Incidence of injury

Recently, a few studies have investigated the frequency of ACL injury specifically in volleyball players. Agel et al3 found that knee internal derangement injuries made up 14% of game injuries and 8% of practice injuries in National Collegiate Athletic Association (NCAA) female volleyball athletes from 1988-2004. Of those internal derangements, 26% were ACL injuries. Athletes had twice the risk of experiencing an ACL injury during a game as they did during a practice; .46 versus .22 per 1000 athlete exposures (an athlete exposure is one athlete participating in one practice or one competition situation).

Based on National High School Sports-Related Injury Surveillance Study data from 2009-2010, girls aged 14 to 18 years had a similar ACL injury rate of 4.5 injuries per 100,000 athlete exposures.4 This data places volleyball number three of four sports in terms of ACL injury rate: rates per 100,000 athlete exposures were 14.1 for soccer, 7.7 for basketball, and 2.3 for softball. Swensen et al5 also looked at high school ACL injury rates, and found a rate of .28 per 10,000 athlete exposures for female volleyball athletes compared with a rate of 0 for male volleyball players. The ACL injury rate for girls in volleyball was lower in that study compared with most other girls’ sports (soccer 1.2 per 10,000 athlete exposures, basketball 1.1, gymnastics 1.1, lacrosse .8, field hockey .3) but equal to the rate found in softball, and higher than that of track and field.

Vauhnik et al6 found volleyball had the lowest rate of ACL injuries (3 per 159,209 hours of exposure) compared with basketball and handball (3 per 33,408 and 6 per 127,673 hours of exposure, respectively) in Slovenian female athletes who played at a highly competitive level. De Loes and colleagues7 found that, overall, cruciate ligament injuries accounted for 14% of all knee injuries in female volleyball athletes aged 14 to 20 years over six years, compared to 11% for male athletes. However, there was no statistically significant difference in injury rate between girls and boys. It is worth noting that De Loes et al didn’t distinguish between injuries to the anterior cruciate ligament and the posterior cruciate ligament.

Within the general public, Majewski et al8 found that 45% of internal knee lesions assessed at a private medical clinic over a 10-year time frame involved the ACL. The researchers identified volleyball as the contributing activity for 3% of those ACL injuries. In that population of individuals aged 10 to 70 years, volleyball, with 47 ACL injuries, ranked fourth behind soccer (580), skiing (533), and handball (128) in terms of absolute numbers of ACL injuries.

Other authors9 found that 14% of the sports injuries presenting to an orthopedic clinic between 1992 and 2006 were specific to the ACL. Volleyball was the reported activity of injury for 39 of the 427 ACL injuries, with women presenting with significantly more ACL injuries than men (34 vs 5). Of the six sports included in the analysis, volleyball ranked third in absolute numbers of ACL injuries after basketball (205) and skiing (136). It’s important to note, however, that this study did not include people who reported participation in more than one sport or activity, individuals older than 50 years, or ACL injury combined with other ligament or meniscus damage.

Overall, it appears the risk of ACL injury in volleyball differs depending on the population. Some findings suggest female athletes are at higher risk than male athletes, but this has not been confirmed in all studies. Although volleyball appears to be a lower-risk sport than others, such as basketball and soccer, ACL injuries still occur and may be preventable. The far-reaching sequelae of an ACL injury, not only for the athlete, but for teammates and families as well, should make prevention a top priority.

Mechanisms and risk factors

Seventy percent of ACL injuries are noncontact, and can involve planting a foot and pivoting, a sudden change of direction, or landing from a jump; all movements that can occur during volleyball.10 There are many factors that contribute to the risk of noncontact ACL injury. They can be divided into intrinsic factors, which are characteristics of the athlete that generally can’t be changed, and extrinsic factors, which can be influenced. Intrinsic factors include joint laxity, ligament notch width,11 and hormone levels.12 Physical conditioning, skill refinement, and neuromuscular control are extrinsic characteristics of the athlete that can be modified13 and therefore are more relevant to those interested in implementing prevention programs.

Table 1: Adapted with permission from reference 43.

Table 1: Adapted with permission from reference 43.

Using video analysis of actual ACL injuries during sports competitions, researchers have identified specific movement patterns that are associated with the injury.14-17 Most often, whether the injury mechanism was landing from a jump or a plant and pivot, the knees were in near extension in a valgus position, and experienced a forceful external or internal rotation.

Athletes need to be educated and undertake training to improve their strength, power, and coordination so that they can avoid these high-risk positions and movements. The sports community must ensure that female athletes are included in these interventions, as studies have shown that they lack the improvement in muscular strength and power, both during and following puberty, that boys experience.18,19 Compared with boys, girls have also shown delayed recruitment of some muscle groups when landing from a jump.20 Without appropriate neuromuscular control, girls may have less influence over their movements than boys during sport activities, potentially putting themselves at risk for injury.

Athlete screening

Screening athletes to identify harmful movement patterns that may increase the risk of ACL injury is a valuable tool that should be used by coaches and team staff. However, at this point, tests specifically aimed at predicting future ACL injury require equipment that most athletes do not have access to (such as an isokinetic dynamometer) or require time and effort that coaches may find inconvenient and impractical.21 Fortunately there are simpler tests available that can highlight movement deficits and potentially help the athlete function more effectively and safely.

The Functional Movement Screen (FMS) test,22,23 for example, has been widely used by healthcare professionals and strength and conditioning staff. It requires basic equipment and can be completed in a timely manner. Although not proven to predict ACL injury specifically, in a recent study including volleyball athletes, a better score on the FMS had a strong correlation with fewer injuries sustained by the athlete.24

Another option is the tuck jump assessment, which requires no equipment (video cameras are optional) and can readily detect movement deficits in a jumping athlete.25 Or, assessment can be as basic as watching an athlete jump down off a box, land, and jump straight back up again as if reaching for an overhead target.26 The assessor should watch the initial landing from a position in front of the athlete to look for a number of frontal plane deficiencies, including a tendency for the knees to migrate medially (valgus position) and for the trunk to deviate from the midline. From a side view, the assessor should watch for a heel-first or flat-footed landing and an erect, extended landing position with minimal flexion in the knees, hips, or trunk. Identification of any of these deficiencies should prompt the coaching staff to develop an intervention program to correct these movement deficits.

Intervention programs

Neuromuscular training programs to decrease the risk of ACL injury take many forms. They include such components as resistance training, plyometrics, flexibility training, and balance exercises, and can be implemented in-season, during preseason, or both. Only two studies have included volleyball athletes in their prospective studies of the effect of exercise prevention programs on ACL injury incidence, and both involved training of female athletes only.

Hewett et al27 had female high school basketball, soccer, and volleyball athletes participate in three 60-to-90 minute training sessions per week for six weeks prior to the competitive season. Training involved plyometrics, flexibility, and weight training. The number of noncontact ACL injuries was significantly lower in the 366 athletes who completed training than in the 463 untrained athletes (0 vs 5 injuries). However, Pfeiffer28 found no statistically significant difference in ACL injury rate between 577 athletes on a 20-minute twice weekly plyometric program undertaken concurrently with their competitive season and 862 athletes in a control group. The study included female high school basketball, soccer, and volleyball athletes. There were six noncontact ACL injuries reported during the study period; none of them occurred in volleyball athletes.

Because the ACL injury rate in volleyball is relatively low, it would be difficult to conduct volleyball-specific studies, as very large numbers of participants would be needed to register enough ACL injuries to ensure sufficient statistical power. Therefore, those involved in volleyball can learn from prevention program research done using athletes from other sports.

Yoo and colleagues29 undertook a meta-analysis of exercise training studies in the literature (mainly involving handball and soccer female athletes) and found, overall, a significant benefit in terms of ACL injury rates to participating in a prevention program. Specifically, the authors found the protective effect was more pronounced for those athletes younger than 18 years, when training was done during both preseason and in-season play rather than one or the other alone, and if plyometric and strength training were included in the training program.

Sugimoto et al30 also undertook a meta-analysis to determine the overall benefit of prevention programs across different sports. They found that 108 athletes would need to participate in an ACL prevention program to prevent one noncontact ACL injury over the course of one competitive season. They also reported that female athletes who did participate in a program had a 73% lower risk of suffering a noncontact ACL injury than those who did not participate.

There are a number of ACL injury prevention programs available to the public. The PEP (preventing injury and enhancing performance) program is freely available online from the Santa Monica Sports Medicine Foundation in California (http://smsmf.org/smsf-programs/pep-program). In two large studies involving high school- and college-aged female athletes, ACL injury rates were shown to decrease markedly with the use of the PEP program,31,32 a 20-minute program designed to replace a standard warm up.

strength-trainThe WIPP (warm-up for injury prevention and performance) program from Sportsmetrics (http://sportsmetrics.org/training-options/wipp/), an ACL injury prevention program developed by the Cincinnati Sports Medicine Research and Education Foundation in Ohio, has a nominal fee associated with it for purchase of an instructional video. In a small study of younger athletes, the 20-minute WIPP program did not seem to improve jump landing patterns.33 However, a more involved program from Sportsmetrics completed three times/week for 90-120 minutes has been shown to decrease injury rates in high school athletes.27 A modified version, designed specifically for volleyball athletes, resulted in improved movement patterns that may help to protect an athlete from injury.34 A recent study has also shown that the improvement in an athlete’s movement as a result of this more intense program can last at least one year.35 However, the degree of improvement does seem to be athlete-specific.

The KLIP (knee ligament injury prevention) program from Boise State University in Idaho is available in the literature.36 Although the KLIP program did not decrease ACL injury rates in high school-aged girls,28 it has been shown to improve landing patterns in college-aged female athletes.36

Other programs that integrate portions of the abovementioned programs, along with variations of other exercises, can also be found freely in the literature.37-40 Coaches can look at the variety of programs available and their effectiveness, and decide what will best fit into their unique sport situation in terms of time and resources.

Most prevention programs involve a combination of strength training, plyometrics, and balance and flexibility training. Little attention has been given to the individual contribution of each of these types of training to the overall prevention of ACL injury, with the exception of Yoo’s work.29 Until more information is available, it would be wise to incorporate all types of training, if possible. The added benefit of participation in an ACL injury prevention program is that evidence exists to suggest that performance is improved as well.37,41

Athlete feedback

As part of a comprehensive ACL injury prevention program, individualized feedback on movement patterns should be provided to athletes, as there is good evidence to suggest this will significantly improve how volleyball athletes land from a jump. Feedback can consist of demonstration and explanation of proper landing mechanics,42 or go one step further and involve the athletes watching video of their own landings to see where they specifically need to improve.

In a study of female volleyball athletes aged 12 to 14 years, the girls landed with increased trunk and hip flexion, even four weeks after a one-time session of individualized verbal and video feedback.43 Because trunk flexion has been associated with decreased ground reaction forces during landing,44 this may be an ACL-protective effect. Coaches may find a checklist of movements useful when reviewing good landing mechanics with an athlete (Table 1).

ACL injuries are serious life-changing events that can occur in any sport that involves jumping or changes of direction. The good news is that athletes and coaches can take preventive steps to significantly decrease the chance of the injury occurring. It will take a concerted effort on the part of athletes, parents, and coaches to make time for an appropriately designed training program to decrease the occurrence of this damaging injury. In the end, the athlete and team may be rewarded with fewer injuries and improved performance.

Joanne L. Parsons, MSc, PT, CAT(C), is a physical and athletic therapist with an interest in sports injury prevention completing her PhD in applied health sciences at the University of Manitoba in Winnipeg, Canada.

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