1. A method for determining 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 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 the coronal plane; electronically identifying the sagittal plane proceeding perpendicular to the identified 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 coronal plane and the identified sagittal plane.