Above-knee prosthetic leg
A lower limb prosthesis for when the knee joint is absent, made up of a socket, a prosthetic knee and a prosthetic foot.
What is an above-knee prosthetic leg?
An above-knee prosthetic leg, clinically known as a transfemoral prosthesis, is a lower limb prosthesis used when the amputation has taken place above the knee joint, at the level of the thigh. Because the person does not have their own knee joint at this level, the functions the knee performs during walking must be taken over by a prosthetic knee system. Compared with below-knee fittings, balance and control come more to the fore, both because the joint has to be recreated and because the residual limb is shorter.
An above-knee prosthesis is an integrated system made up of the socket that encloses the residual limb, the liner between the residual limb and the socket, the prosthetic knee that manages movement and the prosthetic foot that contacts the ground. How well these components work together determines both function and safety in daily activities such as walking, sitting down and standing up, and using stairs and ramps. Because a mismatch in any one component can affect the balance of the whole chain, selection and alignment are approached holistically. The choice of suitable components and knee system is evaluated by the specialist team in line with the person's activity level, safety needs and lifestyle.
The above-knee amputation level
The transfemoral level can be at different heights along the thigh bone. The length and shape of the residual limb and the balance of the surrounding muscles directly affect how the socket is designed and how the prosthesis is suspended. A longer residual limb usually offers a longer lever arm for controlling the prosthesis, while with short residual limbs socket and suspension solutions become particularly important.
In fittings at this level, the quality of contact between the residual limb and the socket is decisive in making the prosthesis feel like a part of the body. For this reason, an above-knee prosthesis is planned not as a sum of individual parts, but as a chain running from the residual limb to the ground whose parts work in harmony with one another.
Main components
An above-knee prosthesis forms a whole through the coordinated work of four complementary main components. How the components behave together determines functionality as much as the qualities of each individual component.
- Socket: The custom-made part that grips the residual limb and transfers the load evenly to it.
- Liner: The intermediate layer between the residual limb and the socket that protects the skin and supports comfort.
- Prosthetic knee: The component that manages movement in walking and balance; the most decisive component at this level.
- Prosthetic foot: The component that contacts the ground during walking and provides balance and support.
What do the components do?
Socket
Made to the measurements of the residual limb; by distributing the load evenly, it helps the prosthesis move in harmony with the residual limb.
Liner
Made of silicone or similar materials, the liner protects the skin against friction and supports comfort inside the socket.
Prosthetic knee
Contributes to the fluidity of walking and to balance by managing the stance and swing phases of the step.
Prosthetic foot
Absorbs the load at the beginning and end of the step; designed for ground contact and balanced push-off.
Prosthetic knee systems: mechanical and microprocessor
Prosthetic knees can generally be considered as mechanical and microprocessor-controlled systems according to their working principles. Mechanical knees provide balance and support with hydraulic, pneumatic or mechanical mechanisms through predetermined settings. Because of their simple structure, these systems may be preferred in many situations of use.
In microprocessor-controlled knees, on the other hand, sensors continuously detect walking and aim to adapt the resistance of the knee to the phase of the step and to the ground. The aim is to support adaptation and safety at different walking speeds and on changing surfaces. Which system is suitable is determined by the specialist team, taking into account the person's activity level, need for balance and general state of health. This content covers system approaches in general, not specific brands or models.
Knee system options
In above-knee fittings, the prosthetic knee is considered in two main groups according to its working principle. Which one is suitable is determined by the specialist team according to the person's activity level, need for balance and general state of health.
Mechanical knee system
Provides balance and support with hydraulic, pneumatic or mechanical mechanisms through predetermined settings. With its simple and durable structure, it is considered in many situations of use.
Learn moreMicroprocessor-controlled knee system
Aims to adapt the resistance of the knee to the phase of the step and to the ground by continuously detecting walking with sensors. It is intended to support adaptation and safety at different speeds and on changing surfaces.
Learn moreStance, swing and safety
The behavior of the knee system in the different phases of the step forms the basis of safe movement.
Stance phase safety
Limiting unintended bending of the knee when weight is transferred to the prosthetic leg supports stable standing.
Swing phase control
Managing the speed of knee bending and extension as the leg is carried forward contributes to a fluid and natural-looking step.
Stumble control
Some systems aim to reduce the tendency to fall forward by providing resistance during unexpected load changes.
Sitting down and standing up
Controlled bending supports balanced and safe movement when sitting down on and standing up from a chair.
Socket and suspension system
The socket is the most personal part of an above-knee prosthesis; it is made according to the shape of the residual limb and determines how the prosthesis sits on it. A well-fitting socket distributes the load evenly to the areas of the residual limb suitable for bearing it and helps the prosthesis move together with the body.
Suspension is the solution that keeps the prosthesis in place without separating from the residual limb during the step. There are different approaches, such as vacuum-based systems, pin-lock mechanisms or belt-like aids. Secure suspension helps the prosthesis stay attached to the residual limb during the swing phase and maintain a consistent position throughout walking. The appropriate suspension solution is evaluated according to the condition of the residual limb, skin structure, activity level and comfort expectations.
Residual limb care and volume changes
The residual limb may show swelling (edema) and volume changes, especially in the early period. Cleaning the skin daily, keeping it dry and checking it for redness, irritation or pressure marks help maintain socket fit. Caring for the liner and socket in accordance with the instructions for use is also important for comfort.
Over time, volume changes in the residual limb may affect the fit of the socket; in this case, temporary adjustments can be made with layers of socks, or the socket may need to be reviewed. If skin irritation that does not heal, pain or a problem with fit is noticed, it is recommended to contact the team that carried out the fitting.
The first prosthesis, getting used to it and gait training
The first prosthesis is usually planned as a transition stage so that the residual limb can take its final shape and the person can become familiar with the prosthesis. The aim during this period is to observe socket fit, establish balance and develop basic walking skills.
Gait training is particularly important in above-knee fittings. Weight transfer, trusting the prosthetic knee, regulating step length and maintaining balance are usually practiced step by step in supported settings such as parallel bars. The rehabilitation process varies from person to person and progresses under the joint guidance of the physiotherapist and the prosthetics team.
Stairs and ramps in daily life
Different surfaces and activities require the knee system and walking skill to be evaluated together.
Stairs and ramps
On sloped and stepped surfaces, controlled bending and balanced weight transfer become important; supports such as handrails can provide confidence.
Changing surfaces
Techniques learned in gait training for maintaining balance on thresholds, slopes and uneven surfaces are carried over into daily life.
Choosing the right knee system
Activity level
The intensity and type of daily mobility are among the main criteria in determining the suitable knee system.
Need for balance and safety
Fall risk and balance needs affect the level of support the system is expected to provide.
Lifestyle
The type of activities at home, at work and outdoors is taken into account in tailoring the choice to the person.
General state of health
Factors such as muscle strength, joint condition and endurance are part of the assessment.
Questions to ask in the consultation when choosing a knee system
When evaluating the options, give examples of specific movements in your daily life. Talk with your practitioner about what the product features mean for your use and which skills training is planned for.
- What kind of training is needed for the stairs at home, the ramp at work and the surfaces I use often?
- How will I use this knee system when sitting down, standing up and changing speed?
- What are the charging, maintenance, water contact and usage limits of the recommended model, and in which user manual can I follow them?
- Which of my needs will we reassess when a trial is done together with the socket and prosthetic foot?
The fitting process
Physician's Prescription / Report
The fitting begins with a specialist physician's prescription/medical report.
Assessment and Measurement
Activity level and the condition of the residual limb are assessed; the suitable knee system, socket and foot are planned.
Production and Trial
A custom-made prosthesis is produced; alignment and fit work is carried out at the trial stage.
Fitting and Gait Training
The prosthesis is fitted; balance and gait training is provided.
Follow-up and Adaptation
Fit is monitored with regular check-ups; adaptations are made when necessary.
Frequently asked questions
Is an above-knee prosthetic leg different from a below-knee prosthetic leg?
Yes. In above-knee fittings, because the person does not have their own knee joint, a separate prosthetic knee system is used. For this reason, balance, control and gait training come more to the fore at this level.
Is a microprocessor-controlled knee suitable for everyone?
Suitability is assessed individually by the specialist physician and team, taking into account activity level, balance and safety needs and general state of health.
How long does it take to get used to an above-knee prosthetic leg?
The adjustment period varies from person to person and depends on the condition of the residual limb and the rehabilitation process. Gait training and regular check-ups support this process.
Is safe movement on stairs and ramps possible?
Controlled techniques for sloped and stepped surfaces are practiced in gait training. The features of the knee system and the person's skill together affect these movements; supports such as handrails can help.
Why does socket fit change over time?
Swelling (edema) and volume changes in the residual limb may affect the fit of the socket. Temporary adjustments such as layers of socks can be made; with permanent changes, the socket may need to be reviewed.
What should be considered in residual limb care?
Keeping the skin clean and dry, checking for irritation or pressure marks and caring for the liner and socket according to the instructions are recommended. If a problem is noticed, the team that carried out the fitting should be contacted.
This content is for information purposes only; consult your physician for diagnosis and treatment. Fittings are carried out at our licensed center addresses in line with a specialist physician's prescription/medical report.
