After arthrography 71 young patients with pain in the knee had a computed tomography (CT) examination. The form of the patella is classified according to the method of Wiberg [12] and on CT 50% of them do not correspond to the type described on the axial roentgenogram. The position of the patella can be examined on CT with a relaxed knee in 15 degrees of flexion. The patellar cartilage is easier to assess on CT: congruity, regularity, imbibition of contrast material and thickness are studied.