Anterior Cruciate Ligament Injuries
Anatomy & Biomechanics
-
completely intraarticular
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anteromedial fibres - tight in flexion - limits anterior translation of tibia on femur
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posterolateral fibres - tight in extension - limits anterior translation PLUS external rotation
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ACL strength = 50% PCL strength
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Load to failure = 1700N
-
strain rate
plays a role in the location of ligament failure
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midsubstance tears occurring at higher rates
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bone ligament complex tears occurring at lower rates
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Blood supply - middle genicular artery (post) & synovial vessels (ant)
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Mechanoceptors with a proprioceptive role
Examination:
Mechanism of Injury:
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substantial anterior tibial shear forces that stress ACL are produced from quadriceps contraction, esp in 0-30 deg of extension
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Typically, the ACL is torn in a noncontact deceleration situation that produces a valgus twisting injury - when the athlete lands on the leg and quickly pivots in the opposite direction.
Associated Injuries:
(
Noyes, 1980
)
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