The anteromedial coronoid facet and the medial lip of trochlea represent one of the most important stabilizing columns of the elbow to prevent posterior dislocation of the elbow. But on average, 58 % of the anteromedial facet extends from the proximal ulnar without sufficient support by the proximal ulnar metaphysic. Some important soft tissue structures insert on the coronoid process. The fracture of anteromedial coronoid facet was recognized recently in clinic as a distinct type of the coronoid fracture. The special injury mechanism is varus posteromedial rotational injury force. This mechanism results in fracture of the anteromedial facet of the coronoid process most often associated with injury of the lateral collateral ligament (LCL) and either subluxation or complete dislocation of the elbow. But the anterior band of the medial collateral ligament is likely to be intact in the complex pattern injury. Standard radiographic evaluation of the fracture includes AP and lateral views of the elbow. Computed tomography, particularly 3D reconstruction, is particularly useful to diagnose the injury. But the LCL injury is easy to be missed, resulting in an earlier traumatic arthrosis. So, it is very important to increase recognition to the pattern injury. If the single distinct converse triangular fragment be found from the film, the surgeon should take care highly, and varus stress x-ray should be necessary to evaluate the LCL injury. Early experience suggests that the injuries should benefit from operative treatment. All injured structures should be repaired to restore the stability of the elbow. Intraoperative testing of the elbow stability is very important.