Prosthetic legs are ideally made of material that is both lightweight and extremely strong. This typically comes in the form of aluminum, titanium or carbon fiber. Those metals may then be covered in other lightweight plastics that help to fill out the pant leg and provide a more natural appearance. The most important part of the limb, though, is the socket which connects the prosthesis to the body of the wearer. The flexible plastic socket is made by an individual called a prosthetist whose job is to ensure that the limb is precisely created so that it mimics the size and motion of the amputated limb as closely as possible. If the prosthetic limb does not fit correctly, it can lead to a number of residual health issues for the wearer.
The prosthetist starts by measuring and taking an impression of the residual limb as well as evaluating the area around which the socket must attach. They then make a plaster cast of the stump which is used to develop a plastic mold. The mold is tested on the limb and modified if necessary to make sure that it has a clean suction and provides the appropriate level of comfort.
Once the prostethist and amputee agree that the mold is a good fit, a final socket is made of flexible plastic that is connected to the stump by suction. The amputee may elect to utilize a gel liner between their skin and the socket if they find it more comfortable. A hard outer shell sits atop the socket for both protection and aesthetics.