Abstract: A prosthetic component with a pneumatic device for knee articulation formed of an upper part adapted to support a socket element for a stump of a thigh, and a lower part intended to receive a tube extended by an ankle and foot. The two parts are connected to each other by an assembly of pivoted links forming a deformable prism. Movement of the two parts between two stable positions of complete extension and flexure, about the variable axis of rotation defined by these connections, is controlled by a pneumatic cylinder having an upper chamber and a lower chamber separated by a piston and communicating with each other by an air duct with adjustable flow. In each of the stable positions, the pressure of air in the chambers is greater than 1 bar and is preferably between 4 and 7 bar.