1. A method a coronal plane and a sagittal plane from a displayed tomographic image of a knee joint, comprising the steps of: displaying a transverse tomographic image of a knee joint, said image being based on an underlying image data set; electronically, automatically analyzing the underlying data set using at least one analysis algorithm to identify the medial condyle and the lateral condyle of the femoral bone head in said tomographic image of the knee joint, and to identify a point at said medial condyle and a point at said lateral condyle that, in combination, define a tangential coronal plane that is tangential to the medial condyle and to the lateral condyle, by identifying a middle point of the femoral bone head into which said coronal plane and said sagittal plane are shifted for acquiring a subsequent slice image, after identification of said tangential coronal plane and said sagittal plane and identifying a circle approximating a shape of a transverse section of the femoral bone head around said femoral bone head and said middle point, and using said middle point as a central point at which said tangential coronal plane and said sagittal plane serve as central planes for acquiring a plurality of plane-parallel slice images of said knee joint; electronically identifying the sagittal plane proceeding perpendicular to the identified tangential coronal plane; and acquiring or representing at least one of a coronal slice image and a sagittal slice image oriented dependent on at least one of the identified tangential coronal plane and the identified sagittal plane.