The triangular fibrocartilage and its function in the kinematics of pronation and supination in the distal radioulnar joint was studied. Measurements of the constituent parts of this joint in 11 cadavers showed that the palmar radioulnar ligament is at least 2 mm longer than the dorsal radioulnar ligament. Based on these measurements the movements of the joint were modelled in a two-dimensional kinematic chain. Predictions based on this chain could be confirmed by direct observation and videotaping dissections of joints of unfixed specimens and three-dimensional reconstructions of a CT scan of a healthy volunteer. It could be concluded that (a) the dorsal part is tight during pronation and the palmar part during supination and (b) considerable asymmetrical translations, (dorsal translation being the largest) occur because of the length differences of the ligaments.