For female athletes, the key to optimal athletic health lies in preventing ACL injuries. In medical terms, the anterior cruciate ligament (ACL) is the primary restraint to the anterior displacement of the tibia on the femur at all angles of the knee flexor.This means when the ACL is injured, the shinbone can slide forward on the thighbone, causing the knee to "give way." The ACL is one of a pair of ligaments in the center of the knee joint that forms a cross or "cruciate." The anterior and posterior cruciate ligaments (PCL) both function to stabilize the knee from front to back. Let's review ACL injuries, why female athletes are more susceptible and how to help prevent ACL injuries in this patient population.
What Causes an ACL Injury?
An ACL injury is usually caused by sudden, abrupt change in force to the knee. This can occur during an unexpected cutting move made during a sporting activity, or while landing following a jump in an athletic activity. Most ACL injuries occur in a non-contact setting and do not involve a collision with another player.1
What Does an ACL Injury Mean to an Athlete?
When an athlete injures the ACL, it may mean losing an entire season of play. If the injury is severe enough, it could also lead to surgery, resulting in long-term rehabilitation, a possible loss of scholarship, and emotional and mental strain. ACL injuries also could pose a lifelong potential for arthritis in the injured joint.2
Why Do They Occur More Frequently in Female Athletes?
ACL injuries typically occur at a four- to six-times higher rate in females because they are more quadriceps dominant. Another factor may be decreased neuromuscular performance and increased ligamentous laxity during menstrual cycles from the fluctuation of female hormones.3-4 A study in The New England Journal of Medicine found differences in leg ailment of males vs. females, noting females have an increased rate of knock-knee (valgus deformity5). The intercondylar notch width is smaller in females, creating less space for the movement of the ACL and resulting in increased risk of injury. Women also typically have a wider pelvis, resulting in thigh bones angling downward more sharply (Q-angle).6 This leads to increased valgus stress and potential injury.
ACL Injuries and Hormones
Fibroblasts lead to collagen synthesis, which enables ligaments and tendons to heal. Estrogen (especially estrodial) inhibits fibroblastic proliferation. Collagen synthesis is significantly reduced with increased local estrodial concentration. Many high-school and college female athletes take birth-control pills, which are all estrogen-based and contribute to the potential for injury.
The National High School Sports-Related Injury Surveillance Study, currently in its fifth year of online data collection, has found that one ACL tear occurs every 15,000 times an athlete practices or competes. On average, athletes are eight times more likely to suffer ACL injuries in competition than practice. Data was collected from a national sample of nine girls' high-school sports, including soccer, basketball, lacrosse, track, volleyball and softball.2
Most Common Sports for ACL Injury in Practice / Competition
- Injuries occur in girls' soccer 1 out of 6,500 times an athlete practices or competes.7
- In girls' basketball, injuries occur 1 of every 11, 000 times an athlete practices or competes.7
ACL Injury Rate Per Sport
A study in the American Journal of Sports Medicine (2009)8 concluded the following with regard to ACL injury prevalence by sport:
- An ACL sports injury prevention training program improved strength and flexibility in competitive female basketball players who were tested.
- The training program also improved biomechanical movement patterns associated with ACL injury as compared with pre- and post-training parameters in the control group.
Of clinical relevance is the conclusion that the prevention program lowered the athletes' risk of injury.
A later study in the American Journal of Sports Medicine (2013)9 concluded that neuromuscular and educational interventions appear to reduce the incidence rate of ACL injuries by approximately 50 percent.
How to Prevent ACL Injuries
The key elements of a clinical program to prevent ACL injury include the following (see examples of each element below):
- Nutrition – supplements and proper diet (discussed in part 2 of this article)
- Dynamic warm-up
- Agility drills
1. Dynamic Warm-Up
- Jog line to line (cone to cone)
- Shuttle run
- Backward running
2. Proper Stretching
- Calf stretch
- Quad stretch
- Figure-four hamstring stretch
- Inner thigh stretch
- Hip flexor stretch
- Glute-ham raise
- Leg curl
- Jump squat
- Single-leg, stiff-legged deadlift
- Bosu plank
- Walking lunges
- Assisted Russian hamstring curl
- Raise or extend hips until torso is perpendicular with legs
- Raise body by flexing knees
- Lower body until horizontal by straightening knees
- Head straight, arms overhead
- Feet pointing straight or slightly toed-out
- Feet slightly wider than shoulder-width apart
- Knees in line with toes
- Squat back, not down
Seated Leg Curl
- Seated vertical, back flat, chest out
- Place lower calves over pad with legs out in front
- Brace upper body, use handles to assist
- Without moving back or hips, pull the pad down and back as far as you can
- Slowly return to starting position
- Start the same as the squat, descend slightly above parallel
- Propel body upward to max height
- Land in similar position, making certain to be soft on the knees
- Note: Do not adduct knees (bring knees together) upon landing
Single-Leg, Stiff-Legged Deadlift
- Stand on one leg, holding weight in both hands
- Keep back flat, lean forward at hips and lift free leg to the rear, in line with the torso
- Touch weight to the ground
- Return to starting position
- Keep back flat and form straight line from head to heels
- Tilt pelvis and contract abs
- Hold for 20-60 seconds
Assisted Russian Hamstring Curl
- Start on knees with arms up and partner holding your feet
- Keeping body straight, slowly lower yourself toward the ground in front until you can no longer hold yourself up
- Push back up with your hands to the upright position
- Repeat 20 times
- Lateral hops over cone
- Forward / backward hops over cone
- Vertical plyo jumps
5. Agility Drills
- Shuttle run with forward / backward running
- Diagonal run
- Bounding run
- Bridging with alternating hip extension
- Single / double knee to chest
- Piriformis stretches
Always use discretion based on the athlete's fitness and desired level of performance. In my next column, I will continue this discussion with tips on nutritional supplementation pre- and post-ACL injury.
- Giugliano DN, Solomon JL. ACL tears in female athletes. Phys Med Rehabil Clin N Am, August 2007;18(3):417-38, viii. See also: Pasanen K, et al. Neuromuscular training and the risk of leg injuries in female floorball players: cluster randomised controlled study. BMJ, 2008;337:a295; published online ahead of print.
- Weekly blog post by Dr. D. Comstock, available on www.training-conditioning.com.
- Spindler KP, et al. Clinical practice. Anterior cruciate ligament tear. NEJM, Nov. 13, 2008;359(20):2135-2142.
- Liu S. Estrogen affects the cellular metabolism of the anterior cruciate ligament. A potential explanation for female athletic injury. Am J Sports Med, 1997;25:704-709.
- Chaudhari AMW, et al. Anterior cruciate ligament-injured subjects have smaller anterior cruciate ligaments than matched controls: a magnetic resonance imaging study. Amer J Sports Med, 2009;37(7):1282-1287.
- Beynnon BD, et al. The effects of level of competition, sport, and sex on the incidence of first-time noncontact anterior cruciate ligament injury. Amer J Sports Med, August 2014;42:1806-1812.
- Statistics courtesy of the American Academy of Orthopaedic Surgeons.
- Lim B-O, et al. Effects of sports injury prevention training on the biomechanical risk factors of anterior cruciate ligament injury in high school female basketball players. Amer J Sports Med, March 2011;37(9):1728-1734.
- Gagnier JJ, et al. Interventions designed to prevent anterior cruciate ligament injuries in adolescents and adults: a systematic review and meta-analysis. Amer J Sports Med, 2013;41(8):1952-62.
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