1. A method for generating a tomographic image, comprising the steps of: placing a patient in a tomographic data acquisition unit and operating the tomographic data acquisition unit to acquire tomographic data representing a first tomographic image of a layer, containing cartilaginous tissue of the patient at a first point in time after subjecting said cartilaginous tissue of the patient to a physical strain at which said cartilaginous tissue still exhibits an effect of said physical strain, said first tomographic image being comprised of pixels; determining a region of said cartilaginous tissue in said first tomographic image; operating said tomographic data acquisition unit to acquire tomographic data representing a second tomographic image of the layer of the patient at a second point in time following said first point in time, at which said effect of said physical strain is no longer exhibited by said cartilaginous tissue, said second tomographic image being comprised of pixels; determining said region of said cartilaginous tissue in said second tomographic image; generating a diagnostic tomographic image, comprised of pixels, by assigning, to each pixel in said diagnostic tomographic image, a difference value between a corresponding pixel of said first tomographic image and a corresponding pixel of said second tomographic image; and in a processor, automatically determining a validation number by adding respective values of all pixels in said region of cartilaginous tissue in said diagnostic tomographic image, and emitting said validation number from said processor as an indicator of a degree of pathology of said cartilaginous tissue.