Female ACL injuries can be prevented by strengthening /balancing muscles.

1. ACL Injuries in the Female Athlete
Prevention Strategies
• 8th Annual Force
Health Protection
Conference
• 9 August 2005

2. Daniel I Rhon, MPT
CPT, United States Army Medical Specialist Corps
Physical Therapist
William Beaumont Army Medical Center

3. Anterior Cruciate Ligament
• One of two internal
stabilizers
• Crucial ligament for
the competitive
athlete

4. ACL ANATOMY
• Necessary for
athletes involved in
cutting and jumping
sports

5. ACL ANATOMY
• Strong ligament – essential for knee stability

6. Tears Common In Contact Sports

7. Incidence of ACL Injuries
• Annually ~ 200,000
ACL tears occur in
the US
• Non-contact ACL
injuries occur most
commonly in both
males & females

8. Noyes et al.
• The Cincinnati Sports Medicine Group
reported that 78% of ACL injuries result
from non-contact mechanisms, most
commonly landing from a jump, cutting,
or sudden deceleration

9. ACL Deficiency
– Often associated with
meniscal cartilage damage
– And articular cartilage
damage
– May not be repairable!

10. Sequelae of Meniscal
Damage
• Experimentally even
partial meniscectomy
increases contact
pressures (up to 350%)!
• Degenerative changes on
X-rays much more
frequent:
75% vs 5%
» Fairbanks, JBJS; 1948:
30B;664-670.

11. ACL Deficiency
• Isolated Tear:
– Relatively easy to
reconstruct
– BUT:
• Season ender
• Patient morbidity
• Prolonged rehab
• Return to form
• Loss to team

12. ACL Tear Risk
• Increased incidence
in female athletes:
– Basketball, volleyball
and soccer
• 4 times greater
than in males!

13. ACL Tear Risk
• Incidence in General population:
– 0.4/1000
• Incidence in high school female athletes:
– 1/100
• Incidence in college female athletes:
– 1/10
• 200-fold increased risk over general
population!

14. Proportional Increase of
Injury?
• Knee injury highest for spring football followed
by:
– Women’s gymnastics
– Women’s soccer
– Men’s wrestling
– Men’s soccer
– Women’s basketball.

15. Increased Rate of ACL Tears
in Female Athletes
• WHY?
– Complex Interactions
– Multifactorial
• Intrinsic Factors
• Extrinsic Factors

16. Impact of Title IX
• Title IX Educational Assistance Act of 1972
– Equal representation of scholastic sports for both
men and women
• Since inception, female participation in athletics has
increased from 300,000 TO 2.37 million

17. Financial Setback
• 1997 Costs for ACL
repair/reconstruction:
- $17,000 (treatment &
rehab)
• Total cost could exceed
$646M / annually for
HS/College athletes

18. Intrinsic Factors
(Not Controllable)
• Smaller size or ACL
• Greater rotatory laxity
• Valgus mal-alignment
• Hyperextension
• Diminished proprioception
• Hormonal influence (estrogen)
• Intercondylar notch shape & width
(White KK., 2003)
(Flynn JM., 2002)

19. Female Anatomic Alignment

20. Physiological Extrinsic Factors
(Modifiable)
Knee stiffness
Activation Patterns
Neuromuscular
characteristics of
dynamic restraints
Landing Differences

21. Knee Stiffness
• Knee stiffness is an important component in
knee joint stability
• External loads applied to knee are resisted by
passive (ligament) and active (muscle)
restraints
• Hence, insufficient muscular stiffness posses
increased risk for ligamentous damage

22. Knee Stiffness
(40 Female Div I athletes, 60 Male football players, 40
controls; male/female)
– Women’s knees looser than men’s
– Women’s Quad and HS weaker (even when body
corrected by height and weight)
– Women more dependent on quad to stabilize knees
• Interestingly: Female athletes no better than
female controls in activating HS to stabilize
knee
Huston and Wojtys, Am J Sports, 1996

23. Knee Stiffness (cont)
• 24 ‘high risk’ athletes compared with 28 ‘low risk’
athlete
– Measured knee stiffness using weighted
pendulum (both with and w/o mm activation)
• CONCLUSION: Collegiate female ‘high risk’ athletes
exhibited less muscular protection of knee ligaments than
did size and sport-matched male athletes
Wojtys et al, 2003

24. Muscle Activation Patterns
FEMALE
Quadriceps Dominant:
- Increases anterior
load seen Anterior
Tibial Translation
- Places increased
stress on ACL
(Antagonist)
MALE
Hamstring Dominant:
- Anterior Tibial
Translation is
Decreased
- ACL load is decreased
significantly (Agonist)
Hewett et al, 1996

25. Preparatory and Reactive
Muscle Activity
• Effectively coordinate muscle activity to protect a joint
requires a quick reaction at the muscle level
• The time taken to generate muscle activity and
produce an adequate force will determine dynamic
stabilization
Lephart et al, 2002

26. Force Production w/shorter
Electromechanical Delay (EMD)
• EMD is the latency period
between preparatory and
reactive muscle activation
• Men have a shorter EMD than
women
• Thus, men demonstrate a
quicker response time for force
production than women
Hakkinen et al, 1991
Osternig et al, 1983

27. Landing Characteristics
• High % of ACL injuries occur when the athlete lands from
jump
– Ground Reaction Force (GRF) 3-14x body weight
• Stiff legged landing increases GRF significantly
– Gender differences seen in knee angles when landing
from jump

28. Landing Characteristics (cont)
• Huston, 2000
– 20 height matched subjects (10 men / 10
women)
– Unconstrained jumps at 20, 40, 60 cm
– Impact Landing: Women averaged 7°
knee flexion compared with Men 16°

29. Land Characteristics (cont)

30. Landing Characteristics (cont)
• Malinzak et al, 1999
• Compared kinematic data on young healthy men and
women during controlled running and cutting
maneuvers
• Results from comparison
– Less knee flexion (25° vs 29°)
– Increased knee valgus (knees pointing inward)
– Less hip flexion

31. ACL Tear Prevention
Is it Possible? YES!!
Several prospective studies have shown an
4 to 8-fold decreased rate on ACL tears in
female athletes who are properly trained
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 Nov-Dec;27(6):699-706.
Mandelbaum BR, et al. AOSSM Annual Meeting, 2002, Disneyland FL

32. Training Program
(Smarter not Harder)
• What now??
• An effective jumping and training program has shown
significant improvements on all previously highlighted
EXTRINSIC FACTORS associated with the increase in
ACL injuries
• Properly trained female athletes can decrease their ACL
tear rate equal to that of males
• Studies show that it can also increase your vertical leap by
10%

33. CD-ROM Exercise Program Demonstration

34. Specificity of Training
is the Key to Injury Prevention
• Still a GREAT program with male
population
• Preventing musculoskeletal injuries with
PROPER exercises should be the
backbone of orthopedic medicine
• Proper education is the forefront to success

35. QUESTIONS?

36. References
• Flynn JM, Lou JE. Ganley TJ. Prevention of sports injuries in children. Current
Opinion in Pediatrics. 14(6):719-22, 2002 Dec.
• Gollehon DL, Torzilli PA. The role of the posterolateral and cruciate ligaments
in the stability of the human knee. A biomechanical study.; Warren-RF J-Bone-
Joint-Surg-Am. 1987 Feb; 69(2): 233-42
• Hewett et al, Plyometric Training in Female Athletes. Am J Sports Med. 1996
• Hewett et al, The Effect of Neuromuscular Training on the Incidence of Knee
Injury in Female Athletes. Am J Sports Med. 1999.
• Huston LJ, Greenfield ML. Wojtys EM. Anterior cruciate ligament injuries in the
female athlete. Potential risk factors. Clinical Orthopaedics & Related
Research. (372):50-63, 2000 Mar.
• Lephart et al, Neuromuscular Contributions to Anterior Cruciate Ligament
Injuries in Females. Rheumatology. 2002.
• Loud KJ, Micheli LJ. Common athletic injuries in adolescent girls. Current
Opinion in Pediatrics. 13(4):317-22, 2001 Aug.
• Messina et al, The Incidence of Injury in Texas High School Basketball. Am J
Sports Med. 1999.

37. References
• Odensten M, Gillquist J. Functional anatomy
• Walsh et. al. Sportsmetric: Neuromuscular Training to Prevent Knee Injuries.
Cincinnati Sports Medicine Research and Education Foundation. 2002.
• White et al, EMG Power Spectra of Intercollegiate Athletes and Anterior
Cruciate Ligament Injury in Females. Med and Sci in Sports & Exercise.
2003
• Wojtys et al. Gender Differences in Muscular Protection of the Knee in
Torsion in Size-Matched Athletes. J Bone and Joint Surg Am. 2003
• Wojtys et al. Neuromuscular Performance in Normal and Anterior Cruciate
Ligament – Deficient Lower Extremities. Am J Sports Med. 1996