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Above-the-Knee Prosthetics

An above-the-knee (also called trans-femoral) amputation is the level of amputation where the femur ,the bone located in the upper half of your leg, is transected. Weight bearing with this amputation is achieved via the ischium bone, the curved bone forming the base of each half of the pelvis, and total contact.

Suspension is how the prosthesis attaches to your leg. Insurance, individual characteristics of your limb and your personal preference are all taken into consideration when deciding on your method of suspension.

Types of suspension

  • Locking pin – A pin is attached to your liner, which engages a lock at the bottom of the socket.
  • Suction – Creates an air-tight seal with a ring on the liner contacting the inside of the socket.
  • Vacuum – Actively draws out the air in the socket to keep your leg securely in the socket.

An above-the-knee prosthesis is comprised of five parts:

  1. Socket – 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.
  2. Liner – 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.
  3. Knee – Prosthetic knees come in many different designs. The main goal of the knee is to stabilize your leg while standing on it and bend while you swing the leg through. Your prosthetist will work with you to determine the most appropriate prosthetic knee for you.
  4. Pylon – The pylon is the shin like portion of your prosthesis that connects the socket to the foot.
  5. 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.