Abstract: Leg prosthesis including a cylinder with a piston and a piston rod, the piston rod being led out of one end of the cylinder and attached to an outer tube of the prosthesis, with the lower part of the cylinder being attached to an inner tube of the prosthesis. The outer tube and the inner tube may be connected to parts of the leg prosthesis, and the cylinder may contain a pneumatic or hydraulic medium. The inner tube and the outer tube provide a cavity for the arrangement of a torsion device, where the outer tube can rotate in both directions in relation to the inner tube and vice versa. The torsion device includes an elastomer fixed to the outer tube, elastomer supports fixed to the outer tube and an elastomer end stop fixed to the inner tube.