What is the ACL?
The ACL also known as the anterior cruciate ligament is one of the major ligaments in the knee. The function of the ACL is to prevent the knee from giving way during twisting, turning and jumping activates. It prevents the shin bone (tibia) from sliding in out in front of the thigh bone (femur). When is the ACL used?

The ACL is primarily used when people participate in twisting, turning and jumping activities it is used in sports such as tennis, soccer, basketball and lacrosse. If the person rides a bike or competes in straight line running, the ACL is not used.

How is the ACL Injured?
There are 2 major ways the Acyl can get torn: noncontact (70%) and contact events (30%). Female athletes tend to tear their ACL with a non-contact event and males with a contact event. An example of a non-contact event would be if an athlete was running down a soccer field and quickly planted one foot to change directions and felt the knee give way. With the giving way episode the ACL becomes disrupted. The tibia slides forward and will pull the ACL off the origin or insertion site in the knee or rupture the ligament mid substance.

Male athletes tend to tear the ACL is with a contact event. An example of a contact event would be a football player getting their leg clipped as they are running down the field by another player.

What are the symptoms that an ACL injury has occurred?
If you answer ” yes” to the 3 questions listed below there is an 85% chance that the ACL is torn: did you hear or feel a pop at the time of the injury, did swelling occur within 12 hours of the injury, and you were unable to finish playing the game? The pop heard at the time of the injury is the ACL being torn in half or being pulled off the side of the bone within the knee joint. The swelling occurs because the ACL is very vascular and bleeds when it is torn. Most people will experience a tremendous amount of pain at the time of the injury and this prevents them from continuing to play. In fact most people will have difficulty walking right after the injury has occurred secondary to pain.

What is the incidence of ACL injuries in the USA?
There are approximately 200,000 ACL related injuries per year in the US and approximately 100,000 ACL reconstruction surgeries per year.

Who needs surgery to reconstruct a torn ACL?
Surgery for an ACL injury is recommended in young people and in people that are active in twisting, turning and jumping activities. The International Knee Documentation Committee (IKDC) has divided activities into 4 categories.

Level 1: Jumping, pivoting, and turning
Level 2: Heavy Manuel work or side to side sports
Level 3: Light Manuel work and non-cutting type sports (cycling and running)
Level 4: Sedentary work without sports
Surgery is not recommended for level 3 and 4 activity per the IKDC.

What is the recovery from this surgery?
The surgery is performed arthroscopically as an outpatient. Most patients are on crutches for 1 to 2 weeks. The rehab phase is intense. Most patients are involved formally with physical therapy 2 to 3 per week and a home exercise program.

Pro athletes are not typically returned back to their sport for at least 1 year after their ACL reconstruction. Most amateur athletes will return back to twisting, turning jumping sports at 5 to 6 months after surgery.

Who tears their Acyl more often: females or males?
The injury rate is much higher for females. Female competitive downhill ski racers will tear their ACL’s twice as much as male racers. There is a reported 8 times higher rate of ACL tears in division 1 female soccer players compared to their male counterparts. There is a 10 time higher rate of ACL tears in the WNBA compared to the NBA.

Why do females tear their ACL so much more than males?
The answer is multifactorial and we are not 100 percent sure. This is one of the most heavily researched areas in sports medicine. What we do know is that before girls and boys go through puberty the ACL injury among the 2 genders is equal. It is after puberty the rate skyrockets for females. Research suggests that females have a quad to hamstring strength mismatch compared to males. Women’s quads can be twice as strong as men’s. The hamstrings prevent the tibia from subluxing forward when the quads are activated. If the hamstrings are weak the quads will pull the tibia forward and allow the ACL to be torn. Think of the hamstring as the muscle group that protects the ACL from being torn. The hamstrings can protect the ACL from being torn by preventing the tibia from being pulled anteriorly (forward) which protects the ligament.

Researchers have found that when females land from a jump, such as a rebound, while playing basketball, they tend to land with their knees in a very straight upright position (less knee flexion) and valgus (knocked knee). Both of these landing positions can cause the ACL to be torn. In addition when they land they tend to have increased quadriceps activation and less hamstring activation compared to their male counterparts. There also may be a hormonal issue regarding the ACL injury. There is some science to suggest that increased estrogen levels may also contribute to the higher injury rate among females.

Can the ACL injury be prevented?

Yes, yes and super yes.

There are now many scientific evidence based published studies that prove that the ACL injury can be prevented. One of the most successful and first programs to be used and published was by Bert, M.D. Mandelbaum et al in the American Journal of Sports Medicine in 2005. Dr. Mandelbaum is the head physician for the Men’s US Pro Soccer league (MLS). In his study they reported a 88% decrease in the ACL injury in the enrolled subjects compared to the control group. They also revealed a 74% reduction in ACL tears in the intervention group compared to age and skilled –matched controls.

In fact the British Journal of Sports Medicine published in 2008 that,” You can prevent the ACL injury. If you have a daughter who is playing basketball, soccer or other field or court sports, then it is crazy if her team is not undertaking one of the evidenced based ACL prevention programs”.

There are programs that can be completed that can help in preventing the ACL injury. The Santa Monica Sports Medicine center has published the most widely used program that has proven results. They did a study looking at high school and division 1 soccer players and found that the ACL injury was reduced by 74%.

What steps can be taken to prevent the ACL injury?

The program is simple, does not require fancy equipment, and is not time consuming. The ACL injury can be prevented with a 15 to 20 minute program that is preformed 3 times per week during the warm-up phase of practice. The program consists of a warm-up, stretching, strengthening, plyometric and sports specific agilities to address potential deficits in the strength and coordination of the stabilizing muscles around the knee joint.

1. www.SMSMF.org
2. info@smsmf.org,
3. www.acl prevention.com
4. www.sportsmetrics.net

References
Arendt, E. et al, The Knee Injury patterns among men and women in collegiate basketball and soccer: NCAA data and review of literature. Am J. Sports Med, 23, 694-701, 1995.

Chappell, J.D., Creighton, R.A., Giuliani, C.,Bing, Y., Garrett, W.E. Kinematics and EMG of landing preparation in vertical stopping, Am J Sports Med, 35, 235-241, 2007.

Ireland, M.L. The Female ACL: Why is it more prone to injury? Orthopaedic Clinics of North America, 33, issue 4., 2002.

Mendelbaum, B.R., 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.

Rentrom. P., Ljungqvist, A., Arendt, E., et al. Non-contact ACL injuries in female athletes: An International Olympic committee current concepts statement. British Journal of Sports Medicine, 42, 394-412, 2008

Roniger, L.R. et al.; ACL prevention program show benefit for teen athletes. J. Biomechanics, 2007