Below-the-knee Prosthetics

A below-the-knee or trans-tibial amputation is the level of amputation where the tibia and fibula (the two bones in the lower part of your leg) are transected. You still maintain a functioning knee joint. Weight-bearing is achieved by total contact and gently applying pressure at specific pressure tolerant anatomical landmarks of the residual limb.

The prosthesis is attached to your leg with suspension. Insurance, individual characteristics of your limb, and your personal preference are all taken into consideration when deciding on your method of suspension. The most common types of suspension available are…

  • Locking pin – has a pin that is attached to your liner. This pin engages in a lock at the bottom of the socket.
  • Suction – creates an air-tight seal with a suspension sleeve on the outside of the socket.
  • Vacuum – actively draws out the air in the socket to keep your leg securely in the socket.

A trans-tibial prosthesis is comprised of 4 main parts:

  1. Socket
  2. Liner
  3. Pylon
  4. Foot

The socket is the term for what your limb will fit into. It is a very important part of your prosthesis as it is what supports your weight. There are many different adjustments that can be made to ensure a comfortable fit inside the prosthesis.

The liner is rolled onto your limb and provides a gel-like cushioned and protective layer between your skin and the socket. They can be made of silicone, urethane, and thermoplastic elastomer (TPE). Socks allow you to adjust the fit of your prosthesis as your limb size changes throughout the day. Socks are worn over your liner and they come in different thickness levels called “ply”. They are used in order to replace the void left as the limb decreased in size throughout the day. Sock management will be an important concept for you to learn as a new amputee.

The pylon is the “shin like” portion of your prosthesis that connects the socket to the foot.

There are many different types of prosthetic feet. Most are made with carbon fiber and are designed for different functions depending on your activity level, hobbies and overall needs.