Imaging techniques for muscle injury in sports medicine and clinical relevance

Abstract

Magnetic resonance imaging (MRI) and ultrasound are the imaging modalities of choice to assess muscle injuries in athletes. Most authors consider MRI as the reference standard for evaluation of muscle injuries, since it superiorly depicts the extent of injuries independently of its temporal evolution, and due to the fact that MRI seems to be more sensitive for the detection of minimal injuries. Furthermore, MRI may potentially allow sports medicine physicians to more accurately estimate recovery times of athletes sustaining muscle injuries in the lower limbs, as well as the risk of re-injury. However, based on data available, the specific utility of imaging (including MRI) regarding its prognostic value remains limited and controversial. Although high-quality imaging is systematically performed in professional athletes and data extracted from it may potentially help to plan and guide management of muscle injuries, clinical (and functional) assessment is still the most valuable tool to guide return to competition decisions.

Fig. 1

a, b, c Different grades of rectus femoris strain depicted on MRI. a Axial Iw FS MRI shows only ill-defined hyperintensity around the myotendinous unit corresponding to mild edema (arrows), without significant associated fiber disruption (grade 1 strain). b Axial Iw FS MRI demonstrates a large well-defined hyperintensity corresponding to an area of intramuscular fiber disruption (arrows) filled by fluid/blood, affecting less than 50 % of the cross-sectional area of the muscle (grade 2 strain). Note the adjacent edema of the remaining fibers of the muscle as well as perifascial fluid. c Coronal Iw FS MRI shows a complete discontinuity of the proximal myotendinous unit (arrow), with a moderate amount of fluid/blood filling the gap (grade 3 strain)

Fig. 2

a, b Dynamic ultrasound assessment of a subacute biceps femoris muscle strain. a Assessment with the muscle at rest shows an ill-defined area of low echogenicity within the muscle (arrows), surrounded by ill-defined areas of increased echogenicity, and it is difficult to affirm the presence of focal fiber disruption. b After concentric contraction of the muscle, ultrasound assessment depicts a well-defined area of lower echogenicity in the same zone, consistent with focal fiber disruption (partial tear)