The invention relates to a passive orthopedic aid in the form of a foot prosthesis or foot orthosis, with a first part which is connected to a second part in a rotatable manner via a swivel joint, with a sensor arrangement for measuring parameters that provide indications of instantaneous operation requirements of the aid, with a control means which is connected to the control arrangement and is used to determine operation requirements and to generate corresponding control signals, with a controllable hydraulic damping arrangement with which a movement resistance acting on the rotation movement between the first part and the second part can be modified, and with a control means which converts the control signals of the processor arrangement and is used to control the damping arrangement. The foot prosthesis is characterized in that the damping arrangement is a dual-action hydraulic cylinder with two hydraulic chambers separated from each other by a piston, and in that the hydraulic chambers are connected via two connection lines which permit a flow of the hydraulic fluid only in mutually opposite directions and whose flow resistances can be adjusted by the control separately and via their own adjustment means each, in that the processor arrangement is configured to determine a current neutral point position from the measured parameters of the sensor arrangement, and in that the control signals for the flow resistances in the two connection lines are generated with respect to the neutral point position.
