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May 26, 2009

Prevent Common Injuries in Soccer: Knee Injuries

Filed under: Sunset Soccer eNews — Tags: , , — sunset @ 6:52 pm

From the U.S. Soccer Communications Center — May 26, 2009

Prevent Common Injuries in Soccer: Knee Injuries

The top four time loss injuries in soccer are ligament injuries (to the ankle and knee) and muscle strains (to the hamstrings and groin). The top injury depends on the level of play. In highly intense, competitive soccer, hamstring strains are being reported as the top time loss injury. In lower levels of play, the lateral ankle sprain is the most common time loss injury. But the injury that leads to the most concern, especially amongst middle and high school aged females, their families and coaches, is an injury to the knee, specifically to the anterior cruciate ligament.

While an injury to the ankle is usually isolated to the lateral ankle ligaments, injury to the knee is far more complex and varied. Injuries can happen to the ligaments, tendons, meniscus, or articular cartilage. This all too brief description may stimulate your interest to learn more about any specific injury.

Ligaments: There are four primary (and a number of supporting) ligaments. The (medial and lateral) collateral ligaments are located on each side of the knee and prevent the knee from collapsing inward (valgus) or outward (varus). The MCL is injured during the classic ‘clip’ in American Football. An injured LCL is pretty rare. Injuries to the MCL and LCL rarely require surgery. The other two, the anterior and posterior cruciates, are located within the joint and restrict rotation and anterior and posterior movement of the tibia under the femur. These are usually injured during over rotation of the tibial alignment with the femur.

Tendon: The main tendon of the knee connects the quadriceps muscle to the patella and tibia. The most common injury is related to overuse, sometimes called a ‘jumper’s knee’. There are reports of the tendon tearing, but this is pretty rare and doesn’t happen to a normal tendon. The problem is no one knows they have a diseased tendon until it tears.

Meniscus: These two crescent moon shaped cups sit on top of the tibia, cushioning the femur. What these discs do is quite complex and injury to a meniscus leads to problems later. Rotation of the femur over the tibia is the usual cause of meniscus injury. If you read of an athlete having arthroscopic surgery and returning to play within a few brief weeks, it’s probably safe to assume an injured meniscus was the surgical target.

Cartilage: Covering the ends of long bones, including the femur and tibia, is a remarkable tissue that protects the underlying bone during movement. Left undamaged, this tissue can last a lifetime. Knee function is severely limited if the articular cartilage is damaged by injury or arthritis. Surgical repair techniques are still evolving. When you read of an athlete retiring because of some generalized knee issue, you could be safe is guessing that articular cartilage damage is at the root of their inability to continue playing.

In a previous post, the research process for injury prevention was presented. First, establish the incidence of injury. Second, determine how the injury happens. Third, devise a prevention protocol and finally, determine if the post intervention incidence is indeed lower.

While there are a number of potential injuries to the knee, most of the prevention programs are directed at preventing ACL injury. What is interesting is that the interest in the ACL is relatively new; the first paper on ACL surgery was published in 1972 and to date there has been nearly 9000 scientific papers published about the ACL. Googling ‘anterior cruciate ligament’ today resulted in nearly 1.1 million hits.

Let’s follow this injury prevention protocol as it has been applied in a few programs specifically designed to prevent ACL injuries. The main locations for ACL prevention research are the Cincinnati Children’s Hospital Medical Center and at two FIFA Medical Centers of Excellence – Santa Monica Orthopaedic and Sports Medicine and the Oslo Sports Trauma Research Centre.

Step 1: Just what is the rate of ACL injury in soccer?
An ACL rupture is certainly is one of the most serious knee injuries in sport, but with surgery and rehabilitation, most athletes return to play within 6-12 months. The actual rate of ACL injury varies according to sex, age, sport and more. More males are injured simply because more males than females play sports. Surgical records of physicians show that ACL injuries in sports are mostly non-existent before puberty. The numbers begin to climb beginning about the age of 14 and peak in high school, and then drop a bit to a plateau during college years before dropping again. Thus, one sees there are essentially three distinct injury rates based on age: 14-18 (middle/high school), college years, post college. Not many studies look at all these age groups and when comparative data are used there comes some error of estimate.

Some of the best sports injury data is contained in the NCAA Injury Surveillance System. For over 15 years, the NCAA catalogued injuries across all sports and divisions and is probably one of the most stable databases on sports injuries in the world. The injury rate for all injuries in male college soccer is 16.4 injuries per 1000 athlete-exposures (1 athlete playing or training for their sport = 1 athlete exposure or A-E). The rate for female players is 5.2. The rate for only ACL injuries is .13 and .31 injuries per 1000 A-E. You can take two things from this basic information. First, ACL injuries are pretty rare. For men, that’s less than 1 percent of all injuries, but higher in women at about 6 percent of all injuries. Second, these numbers show the female/male differences in rate showing the often reported statement that female soccer players tear their ACL at a rate of two to three times more often than males. It’s a pretty rare injury in professional males and only one occurred at the 2006 FIFA World Cup in Germany.

Step 2: How do injuries occur?
ACL injuries can happen from direct contact to the knee, but most often the injury happens in the absence of any direct impact on the knee. The usual description is a rotation of the femur over a fixed tibia when the knee is near full extension. During play, this could be when a player plants their foot and changes direction. A specific and complex sequence of events has to happen to tear the ACL. Most feel that if the knee is near extension and then collapses inwards, the ACL is placed under considerable strain and can tear. When it does tear, the athlete feels immediate pain and instability of the knee. They many even hear an audible ‘pop’ when it ruptures.

Why women have more injuries than men is a matter of intense study. Most reports focus on differences in how women land and cut. Men tend to lower their center of gravity when landing or cutting while women do these in a more erect posture. Cutting or landing on an extended knee places the ACL at risk. As you will see, programs include many activities designed to control the knee during these risky actions.

Step 3: Devise prevention programs.
Many prevention programs have been attempted, but the most effective and successful programs combine core strength and neuromuscular control of the knee during landing and cutting. While each program has some variations in technique, they all have commonalities. For simplicity sake, I’ll briefly describe the program from the only FIFA Medical Center of Excellence in the US, the Santa Monica Orthopaedic and Sports Medicine. You will need to access the detailed instructions at http://www.aclprevent.com/PEPExercises.pdf.

1. Warm-up: Back and forth across the field, jogs, then zigzag run, then jog backwards.
2. Stretch: calf, quads, figure four hamstrings, inner thigh, and hip flexor.
3. Strengthening: walking lunges, Nordic hamstrings (link that word to the hamstring article?), single toe raises.
4. Plyometrics: lateral hops over a cone, forward/backward hops over a cone, single leg hops over a cone, vertical jumps with headers, scissors jumps.
5. Agilities: shuttle run forward and back, diagonal runs, bounding run.

Alternative exercises are offered for variety. These include bridging with alternating hip flexion, abdominal crunches, sitting and double knee to chest, figure four piriformis stretch and seated butterfly stretch.

Once everyone learns the sequence of events, this series of exercises takes about 20 minutes to complete. And these have to be done regularly. None of this ‘one and done’ or ‘two and through’ when it comes to injury prevention; these are an everyday part of training that need to be constantly supervised. Other injury prevention programs can be found in the reference list below.

Step 4: Re-assess injury rate to determine the program’s effectiveness.
Most injury prevention programs lead to overall reductions in injury rates of 30-40 percent. The PEP program described above was conducted over tow years in an entire league of young female soccer players in Southern California. About half the teams chose to follow the PEP plan and the remainder carried out their usual warm-up. The study team recorded all injuries over the full 2 years.

After the 2-year intervention program, the teams who followed the PEP program sustained 30% fewer injuries than the other teams. But most importantly, the intervention teams amazingly had 67 percent fewer ACL injuries. When the program was used in college-aged women, there were 70percent fewer non-contact ACL injuries in the intervention teams. Look at some of the other studies listed in the reference list for other exercises.

What is interesting about prevention programs is that they truly work. Look around at most training sessions and you will probably see well-designed practice plans for skills and tactics, but the weakest part of a training session is likely be the warm-up. So rather than just leave the players to themselves for warm-up, consider a plan that follows some of these programs. You will have a healthier team with fewer injuries better prepared to fulfill your vision of how you want your team to play.

For more information:
At www.FIFA.com, scroll down and click on ‘players health’. Click on the picture that links to The 11, then click on Launch The 11. A list of exercises making up the FMARC 11 is displayed on the left. View the videos and download a poster or instruction booklet.

A newer version of The 11 is available and is called The 11+. Download a poster explaining the program at:
http://www.fifa.com/mm/document/afdeveloping/medical/97/48/07/11+%5fposter2n.pdf

Access the entire PEP program at: http://www.aclprevent.com

References
- Arendt EA. Anterior Cruciate Ligament Injury Patterns Among Collegiate Men and Women. J Athl Train. 1999 Apr;34(2):86-92.

- Dick R. Descriptive epidemiology of collegiate women’s soccer injuries: National Collegiate Athletic Association Injury Surveillance System, 1988-1989 through 2002-2003. J Athl Train. 2007 Apr-Jun;42(2):278-85.

- Ekstrand J. Prevention of soccer injuries. Supervision by doctor and physiotherapist. Am J Sports Med. 1983 May-Jun;11(3):116-20.

- Engebretsen AH. Prevention of injuries among male soccer players: a prospective, randomized intervention study targeting players with previous injuries or reduced function. Am J Sports Med. 2008 Jun;36(6):1052-60.

- Faude O. Risk factors for injuries in elite female soccer players. Br J Sports Med. 2006 Sep;40(9):785-90.

- Gilchrist J. A randomized controlled trial to prevent noncontact anterior cruciate ligament injury in female collegiate soccer players. Am J Sports Med. 2008 Aug;36(8):1476-83.

- Gomes JL. Decreased hip range of motion and noncontact injuries of the anterior cruciate ligament. Arthroscopy. 2008 Sep;24(9):1034-7.

- Hägglund M, Waldén M, Ekstrand J. Lower reinjury rate with a coach-controlled rehabilitation program in amateur male soccer: a randomized controlled trial. Am J Sports Med. 2007 Sep;35(9):1433-42.

- Heidt RS Jr. Avoidance of soccer injuries with preseason conditioning. Am J Sports Med. 2000 Sep-Oct;28(5):659-62.

- Hewett TE. Dynamic neuromuscular analysis training for preventing anterior cruciate ligament injury in female athletes. Instr Course Lect. 2007;56:397-406.

- Junge A. Prevention of soccer injuries: a prospective intervention study in youth amateur players. Am J Sports Med. 2002 Sep-Oct;30(5):652-9.

- Mandelbaum BR. 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 Jul;33(7):1003-10.

- Mountcastle SB. Gender differences in anterior cruciate ligament injury vary with activity: epidemiology of anterior cruciate ligament injuries in a young, athletic population. Am J Sports Med. 2007 Oct;35(10):1635-42.

- Myer GD. Differential neuromuscular training effects on ACL injury risk factors in”high-risk” versus “low-risk” athletes. BMC Musculoskelet Disord. 2007 May 8;8:39.

- Myklebust G. Prevention of noncontact anterior cruciate ligament injuries in elite and adolescent female team handball athletes. Instr Course Lect. 2007;56:407-18.

- Myklebust G. Prevention of noncontact anterior cruciate ligament injuries in elite and adolescent female team handball athletes. Instr Course Lect. 2007;56:407-18.

- Olsen OE. Exercises to prevent lower limb injuries in youth sports: cluster randomized controlled trial. BMJ. 2005 Feb 26;330(7489):449.

- Pasanen K. Neuromuscular training and the risk of leg injuries in female floorball players: cluster randomised controlled study. BMJ. 2008 Jul 1;337:a295.

- Renstrom P. Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement. Br J Sports Med. 2008 Jun;42(6):394-412.

- Silvers HJ. Prevention of anterior cruciate ligament injury in the female athlete. Br J Sports Med. 2007 Aug;41 Suppl 1:i52-9.

- Soligard T. Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial. BMJ. 2008 Dec 9;337:a2469.

- Steffen K. Preventing injuries in female youth football – a cluster-randomized controlled trial. Scand J Med Sci Sports. 2008

- Zazulak BT. The effects of core proprioception on knee injury: a prospective biomechanical-epidemiological study. Am J Sports Med. 2007 Mar;35(3):368-73.

- Zebis MK. The effects of neuromuscular training on knee joint motor control during sidecutting in female elite soccer and handball players. Clin J Sport Med. 2008 Jul;18(4):329-37.

(Dr. Donald T. Kirkendall is on the U.S. Soccer Sports Medicine Committee and a member of the FIFA Medical Assessment and Research Centre.)

Copying, pasting, or other methods of duplication without written permission of U.S. Soccer is prohibited. Copyright 2009. Donald T. Kirkendall. Questions and comments can be directed to coachesnet@ussoccer.org.

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May 5, 2009

Prevent Common Injuries in Soccer: Ankle Sprains

Filed under: Sunset Soccer eNews — Tags: , — sunset @ 12:00 pm

Prevent Common Injuries in Soccer: Ankle Sprains
From the U.S. Soccer Communications Center — May 5, 2009

The top four time-loss injuries in soccer are ligament injuries (to the ankle and knee) and muscle strains (to the hamstrings and groin). Depending on the level of play being studied, the number one common injury changes from the level of player. In elite, highly competitive players, the hamstring strain frequently is reported to be the number one time loss injury. In lower levels of play where the pace of play is slower, the lateral ankle sprain is the most common injury.

In a previous post, the research process for injury prevention was presented. First, establish the incidence of injury. Second, determine how the injury happens. Third, devise a prevention protocol and finally, determine if the post intervention incidence is indeed lower. Let’s follow this protocol as it has been applied to ankle sprains in a project jointly conducted by the EMGO-Institute in Amsterdam and the Oslo Sport Trauma Research Centre, a FIFA Medical Centre of Excellence (Verhagen, 2004).

Step 1: Just what is the rate of ankle sprains in soccer?
As stated, ankle sprains are the most common injury in lower levels of soccer. In a large study of youth and young adult males in Europe, ankle injuries constituted 20% of all injuries (Peterson, 2000). Sixteen percent of all injuries at the 2006 FIFA World Cup in Germany were to the ankle (Dvorak, 2007). The rate of ankle injury in Germany was 11.6 injuries per 1000 match hours, which works out to about one ankle injury about every 2.5 matches.

Step 2: How do injuries occur?
There are two mechanisms of ankle sprains in team sports. The first is a contact injury where a player running with the ball (in this example, the ball is on the player’s right) is challenged by a defender sliding in from the left. The lead foot of the sliding player contacts the inside of the dribbler’s right ankle at or near the time of ground contact. This impact causes the sole of the plant foot to roll inside, damaging the ligaments on the outside of the right ankle.

The other mechanism occurs while landing from a jump. A player jumps, probably to head a ball, and lands on the foot of another player. The unstable landing causes the sole of the foot to roll inwards, damaging the ligaments on the outside of the ankle. This is also how a basketball player sprains an ankle when coming down from a rebound or shot; they land on another player’s foot. A similar occurrence might be when a player steps into a divot in the grass or other such imperfection in the ground.

Injuries to the medial ankle ligaments are rare, but have been reported during hard face-to-face tackling.

Step 3: Devise prevention programs
Programs to prevent ankle sprains have been reported in a number of studies. Verhagen and colleagues (2004) devised a comprehensive program for Dutch volleyball players. The program involved four categories of training exercises: those requiring no equipment, those using a ball, exercises using a balance board, and exercises using the ball on a balance board.

This group studied over 1000 players participating on over 100 teams for an entire competitive season. Teams were randomized into a control group or an intervention group. There were basic exercises for each category as well as variations on each. I highly recommend taking a look at page 1388 of the article for a full description and depiction of the exercises. Most all exercises are performed ten times on each leg (where appropriate). A brief description follows:

Exercises requiring no equipment
Balance on one leg with the other knee flexed. Balance on one leg with the hip and knee flexed. Hold each for five seconds, repeat 10 times on each leg.

Exercises using a ball
In pairs facing each other, balance on one leg with the other knee flexed and toss the ball back and forth (overhand or underhand). Repeat with the hip and knee flexed. Be sure to balance on each leg.

Exercises using a balance board (most commercial balance boards are a round platform attached to the top of what looks like half a croquet ball. Some products have interchangeable bases)
Do the first two exercises (above) on the platform. Try to perform 10 two-legged squats, then try one-legged squats. Walk towards the platform, step on and off while maintaining balance.

Exercises with the board and the ball
Repeat the exercises with the ball, only now on the platform. Repeat while standing on only one leg.

Variations
For variety, the above can be done with the support leg straight or flexed, with the eyes open or closed, tossing the ball over or underhand, or tossing as before with a straight or flexed support leg.

At each training session, the coach would choose one exercise from each of the four categories. No exercise was repeated until all exercises in the category had been used. The total duration needed to complete the four exercises each day was about five minutes.

For example, break the four categories into A, B, C, D. Let’s say there are three exercises per category. The coach might chose exercise one from each category (A1, B1, C1, D1). The next session, they might chose exercise two from each category (A2, B2, C2, D2). The third session, the coach would have to chose exercise three (A3, B3, C3, D3) because the coach can’t go back to exercises one and two (in each category) until exercise three was done. The idea is to force rotation through the exercises and not get stuck on just a set of four and neglect all the rest.

Step 4: Re-assess injury rate to determine the program’s effectiveness.
The overall injury rate did not differ between the control and intervention group. But our interest is in ankle injuries, not all injuries.

There were 41 ankle injuries in the control group and 29 in the intervention group. Based on injury rate, this is a 40% reduction in injury risk in the intervention group. Of specific interest were the injuries in players with a history of ankle sprain vs. those with no history of an ankle sprain. The intervention program had no effect on players without a history of ankle sprain, a finding similar to nearly every previous study on ankle sprain prevention. However, the program was very effective at preventing ankle sprains in those players with a history of sprains.

Paradoxically, the program resulted in an increase in knee injuries, mostly in players with a history of prior knee injury suggesting that as the ankle got stronger, the weak link in the chain shifted from the ankle to the previously injured knee.

Another method of preventing recurrent ankle sprains involves the use of ankle support (Surve, 1994). Those players with a history of a prior ankle sprain who wore the ankle brace had over 80% fewer sprains. In players with no history of an ankle sprain, those who wore the brace had half has many sprains as those who did not wear the brace.

Verhagen’s project presents a comprehensive training program to prevent ankle sprains and it was very effective in preventing the next ankle sprain. No study that examines an exercise program has been effective at preventing the first sprain (the study by Surve just mentioned above used a mechanical brace, not exercises). So, should the coach single out those with an ankle sprain history or just have all players perform the exercise program? It’s probably not a bad idea to incorporate these exercises into a regular warm-up. They are good motor control exercises and all players can use this kind of training. A close look at the FMARC 11 and the 11+ shows that both contain exercises found in this program.

For more information:
To see videos of the balance and motor control exercises at FIFA.com, scroll down and click on ‘players health’. Click on the picture that links to The 11, then click on Launch The 11. A list of exercises is displayed on the left. Each exercise has a description and a link to see a video of the exercise.

For further exercise options, also on FIFA.com, consult the poster for a new version of The 11 that is called The 11+ that can be found here.

References
Dvorak J, A Junge, K Grimm, D Kirkendall. Medical Report from the 2006 FIFA World Cup Germany. Brit J Sports Med 41:578-581, 2007.
Peterson L, A Junge, J Chomiak, T Graf-Baumann, J Dvorak. Incidence of football injuries and complaints in different age groups and skill levels. Amer J Sports Med 28: S51-S57, 2000.
Surve I, M Schwellnus, T Noakes, C Lombard. A fivefold reduction in the incidence of recurrent ankle sprains in soccer players using the Sport Stirrup orthosis. Amer J Sports Med 22:601-606, 1994.
Verhagen E. A van der Beek, J Twisk, L Bouter, R Bahr, W van Mechelen. The effect of a proprioceptive balance board program for the prevention of ankle sprains. Am J Sports Med 32:1385-1393, 2004.

Future postings on how to apply programs to prevent knee and hamstring injuries will be available soon.

(Dr. Donald T. Kirkendall is on the U.S. Soccer Sports Medicine Committee and a member of the FIFA Medical Assessment and Research Centre)

Questions and comments can be directed to coachesnet@ussoccer.org.

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