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Transfemoral & Knee Disarticulation

Recent advancements in socket design and prosthetic knee joints have given many transfemoral (above knee or AK) amputees the opportunity to push the boundaries, transform their lives and regain their independence like never before. P&O Care prosthetists are equipped with the compassion, experience and training to get you back on your feet.

Transfemoral Amputation

A transfemoral amputation involves the removal of the lower extremity above the knee joint.  A prosthetic knee and foot are used to restore function of the lower extremity.

Knee Disarticulaiton

A knee disarticulation involves the removal of the knee joint at the condyles. It is typically considered a “long” transfemoral amputation because a prosthetic knee joint is still required to walk. While there may be differences in socket design and prosthetic knee selection, the treatment of a knee disarticulation and transfemoral amputation and treatment are very similar.

Both transfemoral and knee disarticulation prostheses consist of an intimately fitting socket, prosthetic knee and foot.


The “socket” is the custom made rigid frame made to intimately fit the residual limb. The above knee prosthetic socket is designed to comfortably support the pelvis and body weight during walking. A good socket fit is paramount to prosthetic success and comfort. Learn more about the socket below.

The rotator allows for 360 degrees of rotation below the component at the push of a button. This device helps patients get in and out of cars, tie shoes and get dressed with ease, by allowing the lower half of the prosthesis to be rotated and crossed over the other leg while sitting. The rotator safely locks into the correct position for normal walking. A rotator does add weight and length to the prosthesis, so ask your prosthetist if you have space to add the rotator component to your prosthesis.

Prosthetic knees are designed to replicate the bending or flexion of the anatomical knee joint. From advanced computer controlled components to simple locking joints, there is a prosthetic knee to help all transfemoral and knee disarticulation patients to walk with ease. Learn more about prosthetic knees offered at P&O Care here.

The pylon is the metal component that connects the knee to the prosthetic foot.

Hundreds of prosthetic feet are available on the market today depending on the activity level and goals of the user. Learn more about prosthetic feet offered at P&O Care, here.

A custom shaped foam covering can be made to cover pylon and knee allowing the prosthesis to look similar to your sound side limb and protect the components from dust, debris and outside elements. Covering is usually completed when the prosthetist, patient and medical team are pleased with the fit, comfort and walking mechanics with your prosthesis, which is typically 2-3 weeks after delivery.

Transfemoral Diagram Labeling Socket, Rotator, Knee Joint, Pylon, and Foot - P&O Care - Prosthetic and Orthotic Care

Transfemoral Sockets

The single most important part of any prosthesis is the socket. The socket must fit your residual limb intimately, yet it should be comfortable. Made of lightweight, sturdy carbon fiber materials, this frame must support your full body weight.  The transfemoral socket is designed to support your pelvis, a major bony structure that can handle a large amount of your body weight, and surrounding muscles.  A flexible material is typically used at the very top edges of the prosthesis, so there is a more comfortable transition between the socket and your skin, which is especially helpful during sitting. A well fitting prosthesis enables the user to efficiently move with ease and comfort.  Therefore, each socket must be custom made for each patient, because no two limbs are alike.

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Suspension

“Suspension” is the term used to describe how the prosthesis “suspends” or connects to the residual limb. The most common methods of suspension incorporate some type of gel liner to pad the limb and reduce friction within the socket.  A gel liner is a cushioned envelope that is rolled directly onto the skin and typically made of silicone, urethane or similar material. Some liners even incorporate aloe vera and other minerals to moisturize and protect the skin. There are two modern categories of transfemoral suspension systems using gel liners.

Landyard LockingLiner

A lanyard locking liner has a Velcro strap connected to the bottom of the liner that is fed through passage in the prosthesis. This strap is then looped through a buckle on the outside of the prosthesis and secured (using heavy duty Velcro) to hold it into place. This is a secure and simple suspension system, best for those with reduced hand strength because it is easy to roll on.

Seal in Liner

suctionsealA seal in liner utilizes a “seal” incorporated directly into the liner. The seal is much like a raised donut encircling the bottom half of the limb. When the limb is placed into the prosthesis, the seal is flattened against the wall of the socket. As the limb enters the socket, air is expelled through a one-way valve. Air is not allowed back into the socket and a vacuum (suction suspension) is created. This style of suspension is best for those with excellent hand strength as it can be challenging to roll on the liner due to the presence of the seal on the outside of the liner.

Some suction suspension systems use a one-way valve or “passive” suction system to create suction. This simple valve lets air out of the socket, but not inside the socket. Other suction systems use a more complex pump to quickly evacuate the air out of the system. This is referred to as elevated vacuum or “active” suction. Elevated vacuum was initially designed for use in transtibial prostheses, however recent advancements have made elevated vacuum suspension available for transfemoral applications. Read more about elevated vacuum suspension, here.

Secondary Suspension

Occasionally, your prosthetist may determine that an additional suspension component may be necessary. A cotton or neoprene belt may be added to your prosthesis to ensure that it is secure and functions properly. The belt is attached to the prosthesis and wraps around your waist to ensure the prosthesis is secure.

Resource Center

Our resource center is a great place to learn more about the most complex prosthetic components. We want you to be informed and empowered about your prosthetic future. You have more options than you think, we’ll show you.

5 Most Common Questions About Transfemoral and Knee Disarticulation Prosthetics

Click on the question to reveal answer!

1. Will I need to take off my prosthesis to use the bathroom?

No. You will be able to use the restroom without taking off your prosthesis.

2. Why does the prosthetic socket have to come up so high into my groin?

The transfemoral socket has to go high into the groin to properly support your pelvis, which is a major bony structure that can handle a large amount of your body weight. Since you are no longer able to bear weight on the end of your limb, we need to re-destribute the pressures throughout your residual limb. P&O Care uses a flexible material between the socket and your residual limb to ensure that your skin is protected.

3. Will I need to use a cane or walker with a transfemoral prosthesis?

When you first begin to learn to walk with your transfemoral prosthesis, you will likely use a cane or a walker. As you increase your balance, strength, confidence, you may not need to use an assistive device. Your physical therapist will help guide you through this process. Most transfemoral amputees begin walking with a walker, then graduate to using canes then eventually do not require an assistive device at all. Many above the knee amputees are able to use a transfemoral prosthesis without an assistive device.

4. Will I be able to use stairs with a transfemoral prosthesis?

Yes, absolutely. You physical therapist will teach you how to properly use your prosthesis going up and down stairs.

5. What happens if my limb gets smaller and the prosthesis is too big?

Socks designed specifically for prosthetic use can be used to accommodate for limb shrinkage. There are different thicknesses, or “plys” of socks that can be used to make the prosthesis fit snug again. These cotton socks are put on over the gel liner before your leg is placed in the prosthesis to take up the space lost due to shrinkage.  It is common for your limb to reduce in size and many amputees use socks to ensure a tight fit.

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