1. A method for determining coronal and sagittal planes from a displayed tomographic image of a shoulder joint, comprising the steps of: displaying a transversal tomographic image of a shoulder joint at a monitor, the displayed image of the shoulder joint arising from an underlying image data set; electronically analyzing the underlying image data set of the displayed shoulder joint using a first analysis algorithm to identify, in said shoulder joint, the shoulder blade and to identify two points on the shoulder blade defining the coronal plane; analyzing said underlying data set of said shoulder joint using a second analysis algorithm to identify the shoulder blade and to identify a half-moon shaped arc of the joint connection between the head of the upper extremity of the humerus and the shoulder blade, and to identify two points on said arc at said joint connection that define the sagittal plane; and acquiring tomographic data from, or representing in a further display, at least one of a coronal slice image of said shoulder joint and a sagittal slice image of said shoulder joint, dependent on at least one of the identified coronal plane and the identified sagittal plane.