Polycentric knees, also referred to as “fourbar” knees, are more complex in design and have multiple axes of rotation. Their versatility is the primary reason for their popularity. They can be set up to be very stable during early stance phase, yet easy to bend to initiate the swing phase or to sit down.

What is polycentric knee joint?

A polycentric knee joint is polycentric because the instantaneous centre of rotation between the thigh and the shank changes as the knee flexes. … The polycentric linkage mechanism also allows an increased range of knee flexion and swing control devices of different types can be added.

How does a hydraulic prosthetic knee work?

Hydraulic and pneumatic knees allow adjustment of walking speed by the use of hydraulics (either liquid or air) within the knee. As a person’s walking speed increases or decreases, the hydraulics adjust to control the speed at which the shin of the prosthesis swings forward and bends backward.