An above-knee (AK) prosthesis is a device designed to replace a limb lost above the knee joint. This prosthetic limb restores an individual’s ability to walk, move, and participate in daily activities. Its primary purpose is to enhance mobility and independence for those with a transfemoral amputation.
What is an Above-Knee Prosthesis?
An above-knee, or transfemoral, prosthesis is a device replicating the function of a missing lower limb. The custom socket, molded to fit the residual limb, is the most direct interface with the body. This socket provides suspension and transfers forces, ensuring a secure and comfortable connection.
Extending from the socket is the prosthetic knee joint, which allows for controlled bending and straightening, mimicking natural knee movement during walking. Below the knee, the pylon connects the knee unit to the prosthetic foot. The pylon, made from lightweight, durable materials like carbon fiber, bears the body’s weight and provides the necessary length.
The prosthetic foot is designed to absorb shock, provide stability, and facilitate a smooth transition through walking. Different foot designs offer varying flexibility and energy return, tailored to individual activity levels and needs. Each component works in concert for functional movement and balance.
Different Types of Above-Knee Prostheses
Above-knee prostheses come in several forms, with distinct features for varying user needs and activity levels. Mechanical prostheses, also known as conventional or passive systems, rely on physical mechanisms like springs and friction to control knee movement. These knees are robust and require less maintenance, providing consistent function for basic walking. They offer a straightforward approach, focusing on stability and durability.
Microprocessor-controlled (MPC) prostheses integrate sensors and computer processors within the knee joint. These systems continuously monitor walking speed, terrain, and gait patterns, making real-time adjustments to knee resistance and swing. This adaptive control can enhance stability, reduce the risk of falls, and allow for a more natural, energy-efficient gait across environments. MPC knees are beneficial for individuals navigating varied terrains or desiring higher levels of activity.
Beyond these common types, specialized prostheses are designed for specific activities like running, swimming, or high-impact sports. They feature unique designs, materials, and components optimized for extreme forces and movements. For instance, running blades are flexible and energy-storing, propelling the user efficiently. Selecting a prosthesis type is a collaborative decision between the user and their clinical team, considering lifestyle, goals, and physical capabilities.
The Journey to a Custom Prosthesis
The process of receiving a custom above-knee prosthesis begins with an evaluation by a prosthetist. During this assessment, the prosthetist examines the residual limb’s shape, size, and condition, and discusses the individual’s activity level, lifestyle, and mobility goals. This evaluation ensures the prosthetic design aligns with the user’s requirements.
Following the evaluation, a mold or digital scan of the residual limb is taken to create a custom socket. The socket is the direct interface with the body, and its accurate fit impacts comfort, control, and prosthetic function. The mold serves as the blueprint for a temporary or diagnostic socket.
Trial fittings are then conducted with this diagnostic socket, allowing adjustments for optimal comfort, suspension, and alignment. Several fittings may be involved to refine the socket’s shape and ensure weight bearing and balance. Once the fit is finalized, the definitive prosthesis is fabricated using durable, lightweight materials, with the selected knee joint, pylon, and foot.
The journey culminates with rehabilitation and gait training, guided by physical therapists and prosthetists. This phase teaches effective prosthesis use, focusing on walking techniques, balance, and strengthening exercises. Consistent practice and professional guidance help individuals adapt to the prosthesis and maximize its functional benefits.
Daily Life and Maintenance with an AK Prosthesis
Living with an above-knee prosthesis involves a routine of daily care for both the prosthetic device and the residual limb. The prosthetic socket and liner, which contact the skin, should be cleaned daily with mild soap and water to maintain hygiene and prevent irritation. Inspect the prosthesis regularly for signs of wear, loose components, or unusual noises to identify potential issues early and prevent significant problems.
Care of the residual limb is equally important; daily cleansing and drying are necessary to maintain skin integrity. Check the skin for redness, blisters, or pressure points, as these can indicate an improper socket fit or areas needing adjustment. Addressing these concerns promptly with a prosthetist prevents skin breakdown and discomfort.
Users may encounter minor adjustments or issues over time, such as changes in residual limb volume or discomfort during activities. These require minor modifications to the socket or alignment by a prosthetist. Regular follow-up appointments every six to twelve months are advised to assess the prosthesis’s condition, address ongoing concerns, and ensure it continues to meet evolving needs.
Adapting to daily activities with an AK prosthesis involves learning new ways to perform tasks and developing compensatory movements. While the prosthesis restores significant mobility, some activities require conscious effort and practice. Maintaining a healthy lifestyle, including regular exercise and a balanced diet, supports well-being and helps optimize prosthesis use and comfort.