2nd Annual Sports Medicine Conference
Don G. Aaron, Jr., MD
June 8, 2013
ACL INJURY PREVENTION
I. ACL Anatomy and Function
II. Incidence of ACL Injuries
III.Mechanism of Injury
IV.Risk Factors for Injury
V. Treatment and Rehabilitation
VI.Prevention of Injury
VII.Summary
ACL ANATOMY AND FUNCTION
Anatomy
• The ACL originates at the posteromedial
aspect of the intercondylar notch on the
LFC and inserts on the tibia
approximately 15 mm behind the anterior
articular surface just medial to the
anterior horn of the lateral meniscus.
• There are 2 discrete bands – anteromedial
and posterolateral.
Function
• The ACL is the primary restraint to
anterior translation of the tibia and a
secondary restraint to tibial rotation.
INCIDENCE OF ACL INJURIES
• approximately 95,000
ACL injuries occur each
year (1 in every 3,000
people)
• isolated ACL injuries
account for 50% of all
ligamentous knee injuries
• 70% of injuries occur
during a sporting activity
MECHANISM OF ACL INJURY
Noncontact Injuries
Contact Injuries
• account for 60-70% of ACL
injuries
• most noncontact injuries occur
at footstrike with the knee
close to full extension
• result from sudden
deceleration prior to change of
direction or awkward landing
position
• account for 30-40% of ACL injuries
• occur as a result of valgus
collapse of the knee
RISK FACTORS FOR ACL INJURY
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Anatomic Factors
Neuromuscular Factors
Gender
History of Previous Injury
Genetic Factors
Type of Sport
Extrinsic Factors
RISK FACTORS FOR ACL INJURY
Anatomic Factors
• Knee Geometry
– intercondylar notch width
– posterior tibial slope
– decreased medial tibial plateau depth of
concavity
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ACL Volume
Anterior-Posterior Laxity
Generalized Joint Laxity
Static Alignment of the Lower
Extremity
– valgus knee alignment
• Body Mass Index
– higher BMI in female athletes
RISK FACTORS FOR ACL INJURY
Neuromuscular Factors
• Posture and Landing Biomechanics
• Core Stability
– the body’s capacity to maintain or resume a
relative position after perturbation
History of Previous Injury
• ACL injury < 12 months – 11.3 times
more likely to injure graft or
contralateral ACL
• ACL injury > 12 months – 4.4 times
more likely to injure graft or
contralateral ACL
RISK FACTORS FOR ACL INJURY
Gender
• ACL injuries are 3.5 times greater
in basketball and 2.67 times
greater in soccer for female
athletes
• Reasons:
– anatomic differences
– neuromuscular control
• female athletes land from
jumps and perform agilities
with less hip and knee
flexion, increased knee
valgus, increased internal
rotation of the hip and
external rotation of the tibia,
and increased quadriceps
activation
– sex hormones
RISK FACTORS FOR ACL INJURY
Genetic Factors
• Higher incidence of ACL injury in the
immediate family of injured athlete
(35%) vs. the immediate family of
uninjured athlete (4%)
• COL1A1, COL5A1, and COL12A1 genes
RISK FACTORS FOR ACL INJURY
Type of Sport
• Female soccer – 1 in 6,500
exposures (19%)
• Football – 1 in 9,800 exposures
(41%)
• Female basketball – 1 in 11,000
exposures (13%)
RISK FACTORS FOR ACL INJURY
Extrinsic Factors
• Cleat Design
– Edge design – longer, irregular cleats
placed at the peripheral margin of the
forefoot with smaller pointed cleats
placed interiorly
– Flat design – cleats on the forefoot are
the same height, shape, and diameter
– Screw-in design
– Pivot disk design – 10 cm circular edge
on forefoot with central cleat
• Athletes wearing edge design cleats are 3.5
times more likely to sustain ACL injury
secondary to higher levels of torsional
resistance between the foot and the
ground
RISK FACTORS FOR ACL INJURY
Extrinsic Factors
• Playing Conditions and Surfaces
– dry surfaces > wet surfaces
– artificial surfaces > natural
surfaces
• artificial turf vs. natural grass
(1.5 x)
• indoor synthetic floor vs.
wooden floor (2.35x)
– hot weather > cool weather
TREATMENT AND REHABILITATION
PREVENTION OF ACL INJURY
Identification of “At Risk” Athletes
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female soccer and basketball athletes
football players
athletes with history of previous ACL injury
multivariable model of analysis
PREVENTION OF ACL INJURY
Conditioning and Strength Training
• Goal:
– establish and maintain appropriate
hamstrings to quadriceps strength
relationship
PREVENTION OF ACL INJURY
Prophylactic Bracing
• Controversial
• Largest study involved 1396 cadets and
16 ACL injuries occurred – 4 in the
braced group and 12 in the non-braced
group.
• Study determined that bracing did not
significantly decrease the SEVERITY of
ACL and MCL injuries.
• Human biomechanical studies have
demonstrated that bracing significantly
reduces ACL strain values for anteriordirected shear loading in the weight
bearing and nonweight bearing knee
and internal rotation torque in the
nonweight bearing knee.
PREVENTION OF ACL INJURY
Prophylactic Bracing
• Proper fit is a critical factor
• Most athletes will require
custom fitted braces
secondary to thigh:calf ratio
difference
• The athlete should feel proper
counter pressure at the
proximal tibial strap from 20°
to full extension
PREVENTION OF ACL INJURY
Types of Cleats
• non-edge design cleats
Playing Surfaces
• appropriately irrigated and
maintained practice and
competition surfaces
PREVENTION OF ACL INJURY
Specific Training Protocols
• Balance Training
– series of exercises that involve
having the athlete attempt to
maintain a balanced position
while on a single leg
– results are mixed
• Plyometric/Agility Training
– Santa Monica ACL Prevention
Project or PEP (Prevent Injury,
Enhance Performance) Program
PREVENTION OF ACL INJURY
Santa Monica ACL Prevention Project
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Goals:
– avoiding vulnerable positions
– increasing flexibility
– increasing strength
– including plyometric exercises in training program
– increasing proprioception through agilities
Program should be completed a minimum of 2-3 times per week as a warm-up prior to
athletics
Results:
– athletes that did not perform the program had a 3.3 times greater injury rate
– 88% decreased incidence of injury (32 injuries in untrained group vs. 2 injuries in
trained group)
PREVENTION OF ACL INJURY
SANTA MONICA ACL PREVENTION
PROJECT LINK
http://assets.ngin.com/attachments/document/0004/0565/
The_Santa_Monica_ACL_Injury_Prevention_Project.pdf
SUMMARY
• ACL injuries are extremely
common and debilitating for the
competitive athlete.
• There are multiple risk factors
that must be considered and
modified when possible.
• ACL prevention involves
identification of those athletes
most at risk, employment of
proper strength and conditioning,
use of proper equipment, and
initiation of a PEP Program or
similar protocol.
Go EAGLES
THANK YOU