muscle strain

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Muscle tears or strains are common injuries, both in athletes and non-athletes.

Terminology

Muscle strain is a term that is used variably clinically and in the medical literature. The Munich consensus statement (expert level evidence) states muscle tear is the preferred term denoting "structural injuries of muscle fibers/bundles leading to loss of continuity and contractile properties" .

Pathology

Muscles tears are an indirect muscle injury that occurs in eccentric contraction during sprinting or stretching . Most commonly these injuries occur at the myotendinous junction (MTJ) but can also be peripheral (i.e. myofascial) .

Location

The lower limbs are most of at risk of injury, with biceps femoris the most commonly injured followed by rectus femoris and gastrocnemius muscles .

Radiographic features

Ultrasound

Ultrasound examination may be normal or in low-grade injuries demonstrate focal or diffuse regions of increased echogenicity. Fiber disruption is characterized by well-defined hypoechoic/anechoic regions. Disruption at the myofascial junction or myotendinous junction may be present .

MRI

MRI features corresponding to clinical grades of injury are :

  • grade 1: T2 high signal with a feathery appearance (usually centered on the MTJ) representing edema +/- thickened and high signal of the intramuscular tendon but without laxity +/- mild perifascial fluid
  • grade 2: above features with fiber disruption characterized by high T2 signal and local distortion +/- intramuscular tendon high signal with or without thickening, laxity or partial disruption +/- moderate-severe perifascial fluid
  • grade 3: complete disruption +/- retraction/laxity with local hematoma
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