The differential diagnosis for MR finding of muscle edema is broad. Generalized muscle edema may occur as a result of exercise. Postexercise imaging of muscle demonstrates increase in extracellular fluid and T2 signal and referred to as exercise enhancement [10,121].
Fig. 27. Axial image demonstrates increased fluid signal of myotendinous junction of popli-teus consistent with muscle strain (arrow).
Delayed onset muscle soreness (DOMS) is a clinical entity of muscle soreness and pain after intense exercise (often eccentric contractions) that is usually self-limiting [18,122,123]. It has an MR appearance similar to low-grade muscle strain although abnormal increased T2 signal may persist up to 80 days according to one report . Because of its similar appearance to muscle strain it is often diagnosed clinically. With severe DOMS, muscle necrosis may occur with marked increased signal on fluid-sensitive sequences [18,125].
Muscle edema may also be related to denervation, although this is usually not visualized until the subacute setting  (Fig. 28A). Fibrofatty atrophic changes may be seen in the musculature in patients with chronic denervation related to prior trauma or other muscle damaging process such as acquired or congenital neuropathic disorders (Fig. 28B).
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