Mechanisms of injury

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  Overuse: Strenuous exercise results in diffuse muscular edema

  
  
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  Stretch: Causes torn muscle fibers + hematoma

  
  
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  Direct: Usually blunt trauma causes contusion, ± hematoma, ± tear

Delayed-onset muscle soreness

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  Overuse leads to diffuse muscular edema

  
  
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  Muscle may appear normal or diffusely hyperechoic

Muscle contusion/hematoma

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  Contusion: Ill-defined echogenic muscle; dispersed form of hematoma

  
  
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  Hematoma: Focal hemorrhage often associated with tear

Muscle or myofascial tear

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  Usually partial at/near myofascial junction

  
  
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  Discontinuity ± retraction of fibers filled with hematoma (hematoma can obscure)

Muscle hernia

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  Focal protrusion of fibers through investing fascia

  
  
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  Accentuated by contraction or standing

Tears occur at common locations from common mechanisms

Most injuries improve with conservative treatment and do not require follow-up ultrasound

Clinical symptoms overlap with other diagnoses seen with ultrasound (deep vein thrombosis, tendinosis)

Use contralateral side for comparison; even if bilateral, abnormalities often appear asymmetric

Carefully assess distal medial gastrocnemius for small tears

Use active contraction/passive joint movement to show retraction of fibers