A method for controlling a change of resistance in an artificial joint of an orthosis, an exoskeleton or prosthesis of a lower extremity. The artificial joint has an upper part and a lower part which are secured on each other so as to be pivotable about a pivot axis, a damper unit is secured between the upper part and the lower part in order to provide a resistance to flexion or extension of the artificial joint, and the damper unit is assigned an adjusting mechanism via which the resistance is changed when a sensor signal of a control unit assigned to the adjusting mechanism activates the adjusting mechanism. The resistance is changed as a function of the position and/or length of the measured or calculated leg tendon and/or the time derivatives thereof.