The JT20 polycentric knee joint from Bauerfeind enables adjustment between safe and dynamic geometries. The basis for the system is provided by two centrodes, which can be simply adjusted by turning the excenter. A mechanical spring forwarder and a pneumatic shock absorber – the so-called pre-shock damping – are integrated in the JT20. The interaction of both components allows a harmonic walking pattern. This complex system allows optimal provision for thigh and knee amputees. It has been specially designed for mobility classes 2 and 3, and can carry up to 150 kilograms of body weight.