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Michelle Barber Drover, MSW, DCAssociate Dean, Palmer College of Chiropractic

ACL Injuries in Female Athletes:Theoretical Causes and

Prevention

Image from pxhere.com

ACL: Anterior Cruciate Ligament

Primary stabilizer of the knee

Limits rotation and anterior translation of the tibia

Protects the menisci from shearing forces

2Image from www.southcountypt.com

Length• 22-41mm• Avg 32mm

Width• 7-12mm

Cross-sectional diameter• 36-49mm2

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Image from www.louisville.edu

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“No person in the United States shall, on the basis of sex, be excluded from participation in, be denied the benefits of, or be subjected to discrimination under any education program or activity receiving Federal financial assistance...”

- Title IX of the Educational Assistance Act (1972)

Image from www.womenssportsfoundation.org

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Image from www.womenssportsfoundation.org

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Early opponents of Title IX legislation were concerned that women were

weaker and would have significantly injury rates than men, and

therefore should not be allowed to compete.

This fear was largely unfounded…with one glaring exception.

ACL Injuries/Tears

Non-Contact – usually with landing, rapidly stopping, cutting or change in direction

Altered biomechanical and neuromuscular patterns

Contact vs. Non-Contact

20% contact (football, rugby, ice hockey)

80% non-contact(soccer, basketball, skiing, etc.)

>70% of ACL injuries are sports-related

Often associated with concurrent meniscal injury

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ACL Injury Mechanisms

Hip internally rotated, adducted

Knee near full extension

Tibia externally (or internally) rotated

Foot everted and planted

Body decelerating

Combo of above leads to “Dynamic Knee Valgus” (collapse of the knee)

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8Image from www.physio-pedia.com, adapted from work of Dr. Mary Ireland

Prevention of ACL Injuries

100,000 ACL tears every year

Majority in 15 to 25 year olds

Cost to society 1.5 Billion dollars a year

Short term, loss of participation and game time

Long term, higher chance of arthritis in future

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ACL Injury: The Gender Gap

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• Females

– 4-8x more likely to tear the ACL than males in similar sports

– More likely to have surgery for an ACL injury

– Less likely to return to sports after ACL injury

– 40,000 ACL tears in females/yr

Image from www.daytondailynews.com

Image from contemporarypediatrics.modernmedicine.com 11

Impact of an ACL Injury

• Surgery and/or 6-9 months of rehabilitation

Physical

• Athletes miss whole seasons of play, possible loss of scholarship

• Often limits future sports participation

• Negative impact on academic performance

Social/Academic

• Treatment is $17,000 - $25,000 per injury ($800 million/yr)

Financial

• Despite treatment, 10x rate of early-onset knee OA (15-20 years post injury)

Long-term health

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Factors in Female ACL Injury Risk

Intrinsic (unchangeable)

Extrinsic (changeable)

Combined (potential change)

Joint Laxity Type of Sport Proprioception

Hormonal InfluencesEnvironmental

ConditionsNeuromuscular

Control

Femoral Notch Size ConditioningMuscle Recruitment

Patterns

Ligament Size Strength Core Stability

Limb Alignment Shoes

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Balance of Power• Recruitment Pattern

• Quadriceps muscles antagonist

– stress ACL

• Hamstring muscles agonist

– protect ACL

• Weak hamstrings and strong quadriceps puts ACL at risk

– Female Quad dominant

– Male Hamstring dominant

• Hamstrings 60% to 80% as strong as Quadriceps

Anatomic Factors

Intercondylar Notch

Small notch

Small Ligament size

Intercondylar notch

ACL

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Pantano et al noted that pelvic width to femoral length measurements may be a more accurate structural predictor of

knee valgus and subsequent ACL tension during dynamic activities.

Larger Q-angle tends to place the lower leg into a valgus position resulting in a possible strain on the ACL.

females demonstrate a wider pelvis and a greater average Q-angle.

Q-angle and pelvic width to femoral length ratio

Anatomic Factors: Limb Alignment

Anatomic Factors: Limb Alignment

Environmental Factors

• Fields

• Cleat Design

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Hormonal Factors

• Estrogen and Relaxin

• Relax and soft tissues

• Does this predispose female athlete to ACL injury?

– Increased incidence of ACL tears during ovulatory phase?

Hormonal Factors

Estrogen

• receptors located on the ACL

• reduction of collagen synthesis and fibroblast production

Estradiol and Progesterone

• associated with increased knee and ankle laxity

ACL Injuries Prevention

Biomechanical Factors critical

Neuromuscular/Proprioceptive programs

Plyometric/jump training and Balance drills

Retrain mind on body position

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Prevention Strategies

Greatest success if follow 3 principles:

Plyometrics, balance and strengthening, core

stability, biomechanical feedback

>1x/week Minimum of 6 weeks

Neuromuscular training programs have been shown to decrease ACL injury rates

72% 89% 88% 74% 75%

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ACL Injury Prevention Program: Basic Components

• increase core temp, increase heart rate, and circulation throughout the musculature

Warm–Up (~2 min)

• either dynamic or static Stretching (~2 min)

• focus on the core, hip and thigh regionsStrengthening

(~4min):

• jumping, landing, ballistic movements Plyometrics

(~4 min):

• cutting, changing directions Agility

(~4 min):

ACL Prevention Program

• Improve neuromuscular control and train proper movement patterns

• Gain biomechanical efficiency and accuracy of movement

• Enhance dynamic strength and muscle endurance of the trunk, hip and knee

Goal: the number of ACL tears

• At least 2-3 times per week x 15 min each session

• Replaces the traditional warm-up of practice

• Education for players on strategies to avoid injury

Completed PRIOR TO and DURING sport season

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25Image from orthopropt.com

MANY ACL Prevention Programs out there…

www.smsmf.org/smsf-programs/pep-program

www.aclprevent.com

www.sportsmetrics.net

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References• American Orthopedic Society for Sports Medicine. Hewett TE, Shultz SJ, Griffin LY, Eds. Understanding and Preventing

Noncontact ACL Injuries. Human Kinetics, 2007.

• Beynnon BD, Bernstein IM, Belisle A, et al. The effect of estradiol and progesterone on knee and ankle joint laxity. American Journal of Sports Medicine. 2005 Sep; 33(9): 1298-304.

• Bonci CM. Assessment and Evaluation of Predisposing Factors to Anterior Cruciate Ligament Injury. J Athl Train 1999;34(2):155-164.

• Bosco C, Tarkku L, Komi PV. Effect of elastic energy and myoelectric potentiation of triceps surae during stretch-shortening cycle exercise. Int J Sports Med 1982;3(3):137-140.

• Chandrashekar N, Slauterbeck J, Hashemi J. Sex-based differences in the anthropometric characteristics of the anterior cruciate ligament and its relation to intercondylar notch geometry: a cadaveric study. American Journal of Sports Medicine. 2005 Oct; 33 (10):1492-8.

• Chappell JD, Creighton RA, Giuliani C, Yu B, Garrett WE. Kinematics and electromyography of landing preparation in vertical stop-jump: risks for noncontact anterior cruciate ligament injury. Am J Sports Med 2007;35(2):235-241.

• Dienst M, Schneider G, Altmeyer K, Voelkering K, Georg T, Kramann B, Kohn D. Correltation of intercondylar notch cross sections to the ACL size: a high resolution MR tomographic in vivo analysis. Arch Orthop Trauma Surg 2007;127(4):253-260.

• Draganich LF, Vahey JW. An in vitro study of anterior cruciate ligament strain induced by quadriceps and hamstring forces. Journal of Orthopedic Res. 1990; 8(1):57-63.

• Ford KR, Myer GD, Toms HE, Hewett TE. Gender differences in the kinematics of unanticipated cutting in young athletes. Medicine and Science in Sports and Exercise. 2005 Jan; 37(1):124-9.

• Grindstaff TL, Hammill RR, Tuzson AE, Hertel J. Neuromuscular control training programs and noncontact anterior cruciate ligament injury rates in female athletes: a numbers-needed-to-treat analysis. J Athl Train 2006;41(4):450-456.

• Harmon KG, Ireland ML. Gender differences in noncontact anterior cruciate ligament injuries. Clin Sports Med 2000;19(2):287-302.

• Hewett TE, Lindenfeld TN, Riccobene JV, Noyes FR. The effect of neuromuscular training on the incidence of knee injury in female athletes: a prospective study. Am J Sports Med 1999;27(6):699-706.

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References• Hewett TC, Schultz SJ, Griffin LY. Understanding and Preventing Noncontact ACL Injuries. American

Orthopedic Society for Sports Medicine. Human Kinetics. 2007.• Hewett TE, Stroupe AL, Nance TA, Noyes FR. Plyometric training in female athletes: decreased impact

forces and increased hamstring torque. Am J Sports Med 1996;24(6):765-773.• Ireland ML. The female ACL: why is it more prone to injury? Orthop Clin North Am 2002;33(4):637-651. • Ireland ML. Anterior Cruciate Ligament Injury in Female Athletes: Epidemiology. J Athl Train

1999;34(2):150-154. • Ireland ML, Ott SM. Special concerns of the female athlete. Clin Sports Med 2004;23(2):281-298. • Leetun DT, Ireland ML, Willson JD, Ballantyne BT, Davis IM. Core stability measures as risk factors for

lower extremity injury in athletes. Med Sci Sports Exerc 2004;36(6):926-934. • Liu SH, Al-Shaikh RA, Panossian V, et al. Estrogen affects the cellular metabolism of the anterior cruciate

ligament: a potential explanation for female athletic injury. Am J Sports Med, 1997; 25(5): 704-09.• Mandelbaum BR, Silvers HJ, Watanabe DS, Knarr JF, Thomas SD, Griffin LY, Kirkendall DT, Garrett W Jr.

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(7):1003-1010.

• McClay, I. ACL research retreat: the gender bias, April 6-7, 2001. Clin Biomech (Bristol, Avon) 2001;16(10):937-959.

• McGill, S. Ultimate Back Fitness and Performance. Stuart McGill, 2004.• Myer GD, Ford KR, Hewett TE. Rationale and Clinical Techniques for Anterior Cruciate Ligament Injury

Prevention Among Female Athletes. J Athl Train 2004;39(4):352-364. • Myklebust G, Engebretsen L, Braekken IH, Skjolberg 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(2):71-78.

• Sigward SM, Powers CM. The influence of gender on knee kinematics, kinetics and muscle activation patterns during side-step cutting. Clin Biomech (Bristol, Avon) 2006;21(1):41-48.

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