Rhyou IH, et al. - Researchers intend to ascertain injury mechanisms and soft tissue injury patterns of dislocation caused by posteromedial rotatory instability (PMRI) and simple posteromedial (PM) dislocation of the elbow joint that seems similar on simple radiographs. A retrospective case-series study was designed to include a total of 13 individuals with PMRI dislocation and 10 individuals with simple PM dislocation. In both groups, three-dimensional computed tomography and magnetic resonance imaging were conducted. They distinguished ulnar collateral ligament, lateral collateral ligament complex, overlying extensor muscle, and locus of bone contusion. Thet classified direction of dislocation into the pure-posterior or PM type by simple radiographs. Because of different injury mechanisms, the simple PM and PMRI dislocations of the elbow joint might have different soft tissue injury characteristics.