Tendon and Ligament

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Tendon and Ligament
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Roles of Ligaments and Joint Capsules

• Assist in Stabilization of Joint
• Restrict Movement
• Prevent Excessive Motion

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Roles of Tendons

• Attach muscle to bone
• Transmit tensile loads
• Position of muscle relative to joint

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Mechanical Behavior of Tendons and Ligaments

• Both are viscoelastic tissues
• Visco - a small amount of load results in quite a
  bit of deformation (relative)
• Elastic - refers to Elastic Region
• Importance of viscoelastic qualities?

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Properties of Tendon

• can sustain high tensile loads
• flexible to allow changes in direction of muscle
  pull

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Properties of Ligament

• guides movement
• resists applied force

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Mechanical Propertiesof Tendon and Ligament

• Strength
• Stiffness

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Damage to Tendon and Ligament

• When load is great enough to cause injury, damage
  is dependent on
• rate and
• amount of load

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Load-Deformation Curvefor Tendon and Ligament

• (0,0) - A Toe Region
• A - B Elastic Region
• B Yield Point
• B - C Plastic Region
• C Ultimate Failure Point

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Comparison of Bone toTendon and Ligament

• Identify similarities and differences between
  these tissue types.

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Mechanical Properties ofTendon and Ligament

• Strength
• Stiffness

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Injury Mechanisms

• Injury occurs when tissue is loaded beyond its
  physiological range.
• Microfailure occurs before the yield point is
  reached.

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Injury Mechanisms cont.

• When yield point is exceeded, the ligament begins
  to undergo gross failure.
• Results in abnormal joint displacement
• Displacement results in...

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3 Clinical Categories ofLigament Injury

• Negligible Clinical Symptoms (Grade 1)
• no joint instability can be detected clinically
• Severe Pain (Grade 2)
• joint instability can be detected clinically
• strength and stiffness decreases by 50
• instability can be masked by muscle involvement

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3 Clinical Categories ofLigament Injury cont.

• Severe Pain (Grade 3)
• severe pain experienced during the injury with
  less pain after the injury
• joint is completely unstable
• most collagen fibers have ruptured

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Noyes Study (1977)

• Rhesus monkeys
• 8 wks immobilization
• returned to mobilization
• at 12 mo. mechanical properties were comparable
  to non-immobilized ligaments.
• Drumroll?

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Additional Factors Importantin Tendon Injury

• Amount of force produced by muscle
• Stress comparison between tendon and muscle
• Loading Rates

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Factors Affecting Biomechanical Properties of
Tendon and Ligament

• Aging
• Pregnancy
• Mobilization vs. Immobilization
• NSAIDs

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Osteoarthritis

• Researchers suggest that a deficiency in
  mechanisms that minimize peak forces may cause
  osteoarthritis.