Dorsal defect of the patella.

Of five patients with a dorsal defect of the patella, four were followed for seven to thirteen years. The lesion causes a persistent change in the radiographic appearance of the bone and there may be some residual discomfort in the involved knee. It is best demonstrated on tomograms and on posterior oblique radiographs of the patella. The cause of the defect is unknown and its pathology has not been clearly defined.