Overview of the Components Used in Active and Passive Lower-Limb Prosthetic Devices

This chapter provides an overview of the current state of the art in lower-limb prosthetic componentry, highlighting both the performance capabilities achieved with current limb systems and the limitations that prevent full restoration of function lost due to lower-limb amputation. The overview first covers the socket interface, beginning with designs for supporting weight-bearing loads and suspending the prosthetic limb commonly used in below-knee and above-knee socket systems. This is followed by a presentation of advanced socket componentry for realizing functions such as vacuum-assisted suspension of the prosthesis and accommodation of fluctuations in residual-limb volume. The focus then shifts to passive and active components used in prosthetic foot, ankle, and knee systems. Energetically passive systems are covered first, spanning from purely mechanical designs with and without energy-storage components to microprocessor-controlled designs for both the ankle and knee. The overview concludes with a presentation of current and emerging bionic knee, ankle, and knee-ankle systems that integrate external power and actuation for expanded functional performance.