Three subregions of the infraspinatus are functionally distinct. The superior subregion contributes to abduction, the middle subregion acts as a lateral rotator, and the inferior subregion has both functions.

The aim of this study was to investigate the functions of the six subregions of the supraspinatus muscle (SSP) determined by Kim et al. in Clin Anat 2007;20:648-655, using real-time tissue elastography (RTE). Twelve young male volunteers participated. The muscular hardness of the SSP was measured at rest and with contraction of the MMT3 in internal, neutral and external rotations. The SSP was functionally divided into five groups on the basis of the RTE results. These functional areas were roughly classified into three property groups: the anterior-superficial, anterior-middle, and anterior-deep subregions, which produce contractile force for abduction; the posterior-deep subregion, which produces contractile force for external rotation; and the posteriorsuperficial and posterior-middle subregions, which maintain tension. RTE was appropriate for measuring the functions of these muscular subregions. Clin.