– Written by Kathrin Steffen, Roald Bahr and Grethe Myklebust, Norway (@ostrc1 ; @KathrinSteffen0 )

 “TARPLEY TEARS RIGHT ACL, WILL MISS WOMEN’S WORLD CUP

United States Women’s National Team midfielder Lindsay Tarpley tore her right anterior cruciate ligament in the 75th minute of Saturday night’s 2-0 win over Japan and will miss this summer’s Women’s World Cup in Germany. She is expected to miss six-to-eight months.

This is the same ACL that Tarpley tore in the final game of the 2009 WPS season with the Chicago Red Stars. She slowly recovered from that and made a strong comeback in 2010 with Saint Louis Athletica and, more notably, with the Boston Breakers. Tarpley was recalled to the US team in November and had scored two goals in just four appearances with the team in 2011.”

– equalizersoccer.com

Unfortunately, we hear of numerous sad stories like this, especially among women competing in pivoting sports. Many of these anterior cruciate ligament (ACL) injuries could have been prevented and in this paper we will tell you how.

HOW BIG IS THE PROBLEM?

Severe knee injuries, such as ACL injuries, constitute a serious problem. Unfortunately, they are frequent in many sports. Treatment is costly and it often takes 12 months or more to return to sport or in worst case, lead to early retirement. The long-term outcome is also a concern. A majority of athletes will develop osteoarthritis within 15 to 20 years after an ACL injury, regardless of treatment. Consequently, injuries represent a considerable problem for the athlete, their team and, given the popularity of sport, for society at large.

In football, as in other team sports characterised by sudden changes of direction, pivoting accelerations and decelerations, ACL injuries are a particular concern, especially for female athletes. A recent literature review, including 23 studies, demonstrated that female football players have a two to three times higher ACL injury risk compared to their male counterparts. Females also tend to sustain an ACL injury at a younger age than males¹.

Protecting the health of the athlete by establishing prevention routines early is the responsibility of everyone involved in sports including coaches, medical personnel, referees and the athletes themselves. To maximise the health benefits for players and to minimise the direct and indirect costs associated with injuries, early identification of players at high injury risk is key.

RISK FACTORS

As for most other types of injury, recent studies have suggested that a history of knee ligament injury is the predominant risk factor for a subsequent injury^2,3. However, the reasons for the obvious gender gap in the risk of ACL injury are not completely clear. Various researchers have suggested differences in anatomy, hormonal and neuromuscular function as potential reasons for the higher injury risk in women than in men. To date, however, there is little evidence linking all these potential intrinsic risk factors to noncontact ACL injuries and a great deal of controversy exists on the relative importance of the different factors⁴.

The main external risk factor that has been advanced is the effect of friction between shoes and the playing surface. Investigations from Australian Rules Football and European handball suggest that a high shoe surface friction is associated with an increased risk of ACL injury. For example, when friction is high, the foot can abruptly stop while the athletes are out for a cutting or turning manoeuvre. This will cause the knee to twist suddenly at foot strike and collapse^5,6.

MECHANISMS

ACL injuries usually occur without contact between players and typically during cutting and turning or when landing on one foot after a jump. Even if there is no direct player contact to the knee, many cases involve some sort of perturbation by an opponent (e.g. being pushed slightly off-balance just before landing). The mechanisms for non-contact ACL injuries are widely debated. What seems clear from several studies from various team sports and even alpine skiing is that knee valgus (where the knee collapses inwards into a ‘knock-knee’ position) is an important factor in many cases. This implies that avoiding valgus knee motion is important for preventing injuries^5,7.

PREVENTION

A variety of injury-specific and sport-specific preventive exercise programmes exist. Also, a growing number of programmes have been developed to reduce the risk of knee injuries in general and ACL injuries in particular. Studies from various sports typically show that establishing such programmes as standard warm-up programmes for teams can reduce the risk of injury by as much as 30 to 50%^8-14.

Typically, these programmes consist of exercises focusing on core stability, balance, dynamic stabilisation and muscle strength of the lower extremities. The exercises are often designed as structured warm-up programmes to ensure that all players use the programme regularly. One essential part is to emphasise the ‘hip-knee-toe in line position’ in all types of exercises, both in plyometric, co-ordination and strength exercises. The primary goal of this strategy is to maintain posture and lower limb balance in an attempt to teach players how to control their knee position as far as possible in all situations (Figure 1).

A recent comprehensive review of the scientific literature¹⁵ focused on neuromuscular training programmes developed to alter risk factors associated with an ACL injury and to reduce injury risk in football players. The authors conclude that neuromuscular training appears to be effective in reducing ACL injury risk and that lower extremity strength and balance exercises, in combination with core and trunk control, seem to be necessary components of a successful ACL injury prevention programme. Since Alentorn-Geli et al¹⁵ finished their thorough review, new studies in football have been published which reinforce their message: injuries can be prevented^9,11-13.

We have selected three knee/ACL injury prevention programmes to present all have been proven to prevent 30 to 50% of all injuries (Figures 2 to 4 SEE PDF). Two of the exercise programmes presented here have been developed for football^9,12, while the other is for handball¹⁰. These and other successful knee/ACL injury prevention programmes have several key aspects in common and keeping these in mind, they can easily be adapted to other sports.

PRACTICAL IMPLICATIONS - HOW, WHAT, WHEN?

What type of exercises?

ACL injury prevention works. However, we still do not know how to optimise injury prevention programmes to make them time efficient, which exercises are the ‘right ones’ or if such a thing exists at all.

Balance training alone and home-based training without instruction and feedback on proper movement technique (i.e. lower limb alignment, two-leg landings) is probably ineffective^16,17 unless combined with other types of exercises for core and lower-limb strength, perturbation and jumping, with a continuous focus on knee control.

Another important challenge is to convince coaches and athletes to use the programmes. “Are the exercises really worth doing?” “The programme takes 20 minutes; do we need to do this programme every training session?” These are common questions. And the answers are yes and yes! If done properly, as many as every second injury can be prevented. Perhaps one day, through continued research, programmes can be developed which take less time and are even more effective.

To identify the minimal effective dose to reduce ACL injury risk is a daunting task. Also, we question: Which exercises are the key exercises in a programme: strength, balance, plyometric or agility are actually all of them?

When to start?

Most clinicians and researchers suggest that focus on injury prevention should start as soon as children start participating in organised sports. Generally, injury risk is low under the age of 12¹⁸. Even so, from a motor learning perspective, including exercises to prevent injuries early can help develop ‘good habits’ and less vulnerable movement patters, in addition to establishing correct playing technique and fair play attitudes.

Who should be targeted?

Most prevention programmes today are created as ‘one-size fits all’ package to be performed by all athletes. Perhaps future studies will give more specific knowledge about which type of exercises different sports and different athletes should  perform. Further evidence is needed to determine whether a pre-season functional test e.g. by a drop-jump or single-leg squad test, can be used to identify athletes with higher risk. A study by Soligard et al¹⁹ showed that across different skill attributes, players with high levels of football skills were at greater risk of sustaining injuries than their less skilled teammates. In other words, there are direct and indirect performance benefits from keeping players free of injury.

The Coach is the key!

Winning and performance are the key factors for coaches and players. Therefore, motivating coaches and players to follow exercise programmes is easier if they do not only to prevent injuries but also is provide direct performance benefit²⁰. It might be expected that by implementing a 15 to 20 minute injury prevention programme, physical performance should also improve. However, there is limited research on this with conflicting outcomes²⁰.

Coach education is the key. Well-trained coaches can deliver a new exercise programme in the correct way. Knowledge of sports injuries, injury prevention, attitudes and beliefs to the importance of injury prevention training is quite varied among coaches. Without doubt, injury prevention should be mandatory as part of the coach education and certification at all levels.

TAKE HOME MESSAGE

It is possible to prevent ACL injuries, however, much research is still needed to make the current programmes even better and maybe more athlete-specific. We know that exercise programmes need to include a combination of balance, co-ordination, strength, plyometric and agility exercises. A better understanding of ACL injury risk factors and mechanisms will help us to optimise current injury prevention programmes. In the meantime, our best recommendation is to establish warm-up routines and put the existing knowledge on ACL injury prevention into practice. Spread this knowledge and convince coaches and athletes that ACL prevention works!

Kathrin Steffen Ph.D.

Grethe Myklebust P.T., Ph.D.

Research and Knowledge Translation

Oslo Sports Trauma Research Center

Norwegian School of Sport Sciences

Oslo, Norway

Contact: kathrin.steffen@nih.no

Website: www.ostrc.no; www.skadefri.no

Roald Bahr M.D., Ph.D.

Sports Medicine Physician

Aspetar – Qatar Orthopaedic and Sports Medicine Hospital

Doha, Qatar

References

1. Waldén M, Hägglund M, Magnusson H, Ekstrand J. Anterior cruciate ligament injury in elite football: a prospective three-cohort study. Knee Surg Sports Traumatol Arthrosc 2011; 19:11-19.
2. Waldén M, Hägglund M, Ekstrand J. High risk of new knee injury in elite footballers with previous anterior cruciate ligament injury. Br J Sports Med 2006; 40:158-162.
3. Steffen K, Myklebust G, Andersen TE, Holme I, Bahr R. Self-reported injury history and lower limb function as risk factors for injuries in female youth soccer. Am J Sports Med 2008; 36:700-708.
4. Renström P, Ljungqvist A, Arendt E, Beynnon B, Fukbayashi T, Garrett W et al. Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement. Br J Sports Med 2008; 42:394-412.
5. Olsen OE, Myklebust G, Engebretsen L, Bahr R. Injury mechanisms for anterior cruciate ligament injuries in team handball: a systematic video analysis. Am J Sports Med 2004; 32:1002-1012.
6. Meyers MC, Barnhill BS. Incidence, causes, and severity of high school football injuries on Field Turf versus natural grass: a 5-year prospective study. Am J Sports Med 2004; 32:1626-1638.
7. Koga H, Nakamae A, Shima Y, Iwasa J, Myklebust G, Engebretsen L, et al. Mechanisms for noncontact anterior cruciate ligament injuries: knee joint kinematics in 10 injury situations from female team handball and basketball. Am J Sports Med 2010; 38:2218-2225.
8. Mandelbaum BR, Silvers HJ, Watanabe DS, Knarr JF, Thomas SD, Griffin LY 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; 33:1003-1010.
9. Soligard T, Myklebust G, Steffen K, Holme I, Silvers H, Bizzini M et al. Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial. BMJ 2008; 337:a2469.
10. Myklebust G, Engebretsen L, Braekken IH, Skjølberg A, Olsen OE, Bahr R. Prevention of anterior cruciate ligament injuries in female team handball players: a prospective intervention study over three seasons. Clin J Sport Med 2003; 13:71-78.
11. LaBella CR, Huxford MR, Grissom J, Kim KY, Peng J, Christoffel KK. Effect of neuromuscular warm-up on injuries in female soccer and basketball athletes in urban public high schools: cluster randomised controlled trial. Arch Pediatr Adolesc Med 2011; 165:1033-1040.
12. Waldén M, Atroshi I, Magnusson H, Wagner P, Hägglund M. Prevention of acute knee injuries in adolescent female football players: cluster randomised controlled trial. BMJ 2012; 344:e3042.
13. Kiani A, Hellquist E, Ahlqvist K, Gedeborg R, Michaëlsson K, Byberg L. Prevention of soccer-related knee injuries in teenaged girls. Arch Intern Med 2010; 170:43-49.
14. Olsen OE, Myklebust G, Engebretsen L, Holme I, Bahr R. Exercises to prevent lower limb injuries in youth sports: cluster randomised controlled trial. BMJ 2005; 330(7489):449.
15. Alentorn-Geli E, Myer GD, Silvers HJ, Samitier G, Romero D, Lázaro-Haro C et al. Prevention of non-contact anterior cruciate ligament injuries in soccer players. Part 2: a review of prevention programs aimed to modify risk factors and to reduce injury rates. Knee Surg Sports Traumatol Arthrosc 2009; 17:859-879.
16. Söderman K, Werner S, Pietila T, Engström B, Alfredson H. Balance board training: prevention of traumatic injuries of the lower extremities in female soccer players? A prospective randomised intervention study. Knee Surg Sports Traumatol Arthrosc 2000; 8:356-363.
17. Engebretsen AH, Myklebust G, Holme I, Engebretsen L, Bahr R. Prevention of injuries among male soccer players: a prospective, randomised intervention study targeting players with previous injuries or reduced function. Am J Sports Med 2008; 36:1052-1060.
18. Froholdt A, Olsen OE, Bahr R. Low risk of injuries among children playing organized soccer: a prospective cohort study. Am J Sports Med 2009; 37:1155-1160.
19. Soligard T, Grindem H, Bahr R, Andersen TE. Are skilled players at greater risk of injury in female youth football? Br J Sports Med 2010; 44:1118-1123.
20. Lindblom H, Waldén M, Hägglund M. No effect on performance tests from a neuromuscular warm-up programme in youth female football: a randomised controlled trial. Knee Surg Sports Traumatol Arthrosc 2011; 20:2116-2123.

Image via University of Fraser Valley