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Materials Used in the Prosthesis. A variety of materials can be used for the manufacture of artificial limbs. Wood, especially willow, is the most popular because it is comparatively light and resilient, and is easily shaped. Aluminum or an aluminum alloy is used when lightness is particularly desirable, such as in a limb for an aged person. Plastic limbs are also available. Leather and various metals are used for reinforcement and control.

Powering the Limb. Most artificial limbs are powered by the muscles, either those remaining in the residual limb or other available muscles. The muscles of the residual limb often can be considerably strengthened by physical therapy. Muscle power can be reinforced by means of springs, straps, gears, locks, levers, or, in some cases, hydraulic mechanisms.

The Artificial Lower Limb. The most commonly fitted artificial limb is the knee-jointed leg, used by persons whose lower limbs have been amputated above the knee. This prosthesis is powered by the hip and remaining thigh muscles, which kick the leg forward. The key points in such a limb are the socket, where it fits onto the residual limb, the knee, and the ankle. The possibility of walking with a normal gait depends primarily on the successful alignment of the socket joint; the knee usually consists of a joint centered slightly behind that of the natural leg, as this has been found to afford greater stability; sometimes the ankle joint is omitted and flexibility of the ankle achieved by the use of a rubber foot.

The Artificial Upper Limb. The choice of a particular artificial upper limb depends largely on the person's occupation. There are many different types, ranging from the purely functional, which will enable a person to perform heavy work, to the purely cosmetic, which aims only at looking as natural as possible. Those persons whose work requires them to do heavy lifting are often fitted with a “pegarm,” a short limb without an elbow joint, which is easily controlled and has great leverage.

The Artificial Hand. There are many different types of artificial hands. Many artificial upper limbs are so constructed that they can be fitted with a selection of different hands, depending on the type of work to be done. Researchers generally agree that the various types of hooks offer the greatest functional efficiency. These reproduce the most powerful function of natural hands—the pressure between thumb and forefinger. There are also artificial hands that combine a certain amount of utility with cosmetic value, often by means of a cosmetic glove covering a mechanical hand; others are designed simply for appearance, though they may offer some support as well.

Most hooks and hands are mechanically connected to the opposite shoulder and operated by a shrugging motion. However, a procedure known as kineplasty uses the person's own arm and chest muscles to work the device. In this method, selected muscles are tunneled under by surgery and lined by skin. Pegs adapted to the tunnels can then be made to move an artificial hand mechanism. Kineplasty is used when skill rather than strength is desired.