In this prosthesis for pneumatic knee joints, iglidur® J piston rings replace the previously used PTFE guide bands. They absorb radial forces and assure the piston a light, low-friction guide, which affects the swing phase of the joint. The piston rings can be clipped quickly and easily. This reduces installation time and assembly costs. After successful tests of the iglidur® J piston rings, the wear and tear was barely noticeable. The functionality, quality and durability of the knee joint are increased. Moreover the important gliding properties are considerably enhanced.