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Chapter 3
 Mechanism of Injury- how an injury occurs
 Severity of Injury depends on:
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Type and angle of force; different periods of
time
Tissue affected- bone, muscle, tendon, ligament
Force and Its effects
 Force = the push or pull acting on a body
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Two possible outcomes:
• Athletes can apply force
• Athletes can absorb force
 Types of force-Fig 3-1
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Axial = acting along the long axis of a structure,
• Compressive = squeezing or crushing a structure
• Tension = pulling or stretching on an object
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Shearing = parallel or tangent to a structure-spine
Torque = force around an axis-elbow/shoulder
Force and Its effects
 Failure = the loss of continuity of a tissue
resulting in rupture or fracture
 Stress = distribution of force within a body
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Force/area – Fig 3-2
Force has a greater stress on a smaller area of
the body
A higher amount of stress, rather than a higher
amount of force usually c/s injury
Force and Its effects
 Types of injury
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Acute = mactrotrauma-fracture, sprained ankle
• Definitive moment of onset and single force
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Chronic = microtrauma-stress fractures,
arthritis
• Repeated chronic loading over a period of time
• Can persist for months or even years
• Acute injuries can turn into chronic injuries
Healing of Soft Tissue (1)
 Three phases
 Phase 1 = acute inflammatory - 0-6 days
 Phase 2 = repair and regeneration 3-21+
days (Proliferation)
 Phase 3 = remodeling up to 1+ year
(Maturation)
Tissue Healing Phases
Acute Inflammation Phase
 First several days after injury
 Key signs:
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Redness, heat, swelling, pain, loss of function
 Key events:
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Vasoconstriction --- tissue death (necrosis)-last secs to
10 minutes- reduces blood loss at a tissue site b/c blood
thickens
• Blood Clotting Mechanism- Platelet reaction-Fig 3-3
• Chemical mediator release- aid in the inflammation processcause pain by stimulates nerve endings
Inflammation Process Continued
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Vascular permeability increases/ vasodilation of
cells which allows exudate to cleanse the site of
debris and infectious materials
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Exudate-plasma like substance that is made up
of protein and WBC

Hematoma and Edema formation
Repair and Regeneration
 3 days – 6 to 8 weeks
 Begins when hematoma is diminished to
allow for growth of new tissue
 Key events:
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Scar tissue formation begins
Improved vascularization
Collagen is laid down
Remodeling Phase
 3 weeks after injury – up to one year
 Mobilization vs immobilization
 Key events:
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Maturation of tissue-increases strength
Collagen fibers oriented along lines of stress
Decreased Flexibility
Return to normal chemical activity within body