Ligaments and Tendons

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Ligaments and Tendons
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Ligaments

• Augment the mechanical stability of joints
• Guide joint motion
• Prevent excessive motion

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Tendons

• Attach muscle to bone
• Transmit tensile loads from muscle to bone

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Composition

• Dense connective tissue (parallel-fibers of
  collagen)
• - Sparsely vascularized
• Cellular (fibroblasts) 20
• Extracellular (80)
• - 70 H2O
• - 30 solids collagen, ground substance, elastin

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Composition

• Collagen
• - ligaments - 75 of solids
• - tendons 75 of solids

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Ligament/Tendon Schematic
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Ligament/Tendon Schematic
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Ligament versus Tendon
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Tendon - Structure and Function

• sustain high tensile forces
• flexible

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Ligament - Structure and Function

• pliant and flexible
• strong and inextensible/inelastic

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Injury is affected by

• Rate of impact
• Amount of load

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Tendon
3
4
2
1
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ACL Injury
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ACL Injury
Microfailure
Load
Complete Failure
Physiological Loading
Injury
Joint Displacement
Clinical Test
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Ligamentum Flavum
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Factors affecting Mechanical Properties

• Maturation
• - ?20 ? quality of cross-links ?? ? tensile
  strength and ?collagen fiber diameter
  (hypertrophy)

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Factors affecting Mechanical Properties

• Aging
• collagen content ? ? ? stiffness, strength
  ability to withstand deformation
• Pregnancy and postpartum
• tensile strength stiffness in tendons ?

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Factors affecting Mechanical Properties

• Physical Training
• - ?tendon tensile strength and ligament-bone
  interface strength
• - ligaments become stronger and stiffer,
  collagen fibers increase in diameter

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Factors affecting Mechanical Properties

• Immobilization
• - ? tensile strength of ligaments, more
  elongation, less stiff
• - ? in cross-links
• -After 8 weeks of immobilization ? 12 months to
  recover strength stiffness

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Effects of Immobilization
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Effects of Immobilization
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Effects of Immobilization
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Factors affecting Mechanical Properties

• NSAIDS
• - ? tensile strength possibly due to ?
  cross-linkage
• Local Cortisone
• - alters collagen organization in tendon
• - random versus parallel