Prosthetic Leg Components Explained: A Guide to How a Prosthetic Leg Works

If you are considering getting a prosthetic leg, or you have already been prescribed a lower limb prosthesis, you probably have many questions. How does a prosthetic leg work? What are the different prosthetic leg components? Which parts of the prosthesis are most important for comfort and mobility?

Understanding the basic parts of a prosthetic leg can help you feel more confident throughout your rehabilitation journey. Below, we'll explain the main prosthetic leg components, how they work together, and why each plays an important role in helping you walk comfortably and safely after amputation.

What is a Prosthesis?

A prosthesis (plural: prostheses) is an artificial device designed to replace a body part that has been lost due to amputation, trauma, disease, or a congenital limb difference. When the prosthesis replaces part or all of a leg, it is known as a prosthetic leg, artificial leg, or lower limb prosthesis.

A modern prosthetic leg is made up of several specialised components that work together to restore mobility, improve balance, increase comfort, and help individuals return to their daily activities with greater confidence.

The Prosthetic Socket

The prosthetic socket is often considered the most important component of a prosthetic leg. It connects your residual limb (sometimes called a stump) to the rest of the prosthesis and forms the foundation of the entire system.

A well-fitting socket is essential for comfort, stability, and successful prosthetic use. An ill-fitting socket can lead to discomfort, skin irritation, reduced mobility, and difficulty wearing your prosthesis for extended periods.

Because every residual limb is unique, each prosthetic socket is custom designed and manufactured by your prosthetist to match your individual limb shape, anatomy, soft tissue, and skin characteristics. This personalised fit helps optimise comfort, weight distribution, and control while walking.

The Prosthetic Liner

The prosthetic liner is a soft, flexible interface worn between your skin and the prosthetic socket. It cushions the residual limb while protecting your skin from friction, pressure, and shear forces during everyday movement.

Choosing the right prosthetic liner is essential for achieving a comfortable, secure fit and maintaining healthy skin. Together, the liner and socket help provide suspension, improve comfort, reduce movement inside the socket, and enable your prosthetic leg to function effectively throughout the day.

Different liner materials and designs are available, and your prosthetist will recommend the most suitable option based on your activity level, residual limb shape, skin condition, and rehabilitation goals.

There are three main ways to attach a liner to your socket: 

• Locking liner: a locking pin at the end furthest from the residual limb  
• Cushion liner: an extra layer applied over the liner and socket  
• Seal-in liner a vacuum with a seal  

Prosthetic Knee

Whether your prosthetic leg includes a prosthetic knee depends on your level of amputation. People with an above-knee (transfemoral) amputation require a prosthetic knee, while those with a below-knee (transtibial) amputation do not.

A prosthetic knee is designed to replicate the function of a natural knee by providing stability while standing, smooth and controlled movement during walking, and the flexibility needed for everyday activities such as sitting, climbing stairs, navigating uneven ground, and, in some cases, kneeling.

As one of the most complex joints in the human body, the knee performs thousands of coordinated movements every day. Recreating this function in a prosthesis requires advanced engineering to deliver both safety and natural movement. A well-selected prosthetic knee helps improve balance, walking efficiency, confidence, and overall mobility while reducing the amount of energy required to walk.

If a prosthetic knee is not suited to your lifestyle, activity level, or mobility goals, it can affect your gait, place additional strain on your hips and lower back, increase fatigue, and potentially raise the risk of falls. This is why selecting the right knee joint is an important part of successful rehabilitation.

Types of Prosthetic Knees

Modern prosthetic knees generally fall into two main categories:

• Mechanical prosthetic knees use springs, hydraulic or pneumatic systems to provide stability and control. They are durable, reliable, and available in a range of designs to suit different mobility levels.
• Microprocessor-controlled (bionic) prosthetic knees use onboard sensors and computer technology to continuously monitor your movement and automatically adjust resistance in real time. These advanced knees can improve stability, reduce the risk of falls, and create a smoother, more natural walking experience across a variety of terrains.

Your prosthetist will assess factors such as your amputation level, activity level, lifestyle, strength, balance, and rehabilitation goals to recommend the prosthetic knee that best meets your individual needs.

Click here to explore our prosthetic knees.

Prosthetic foot 

The prosthetic foot is one of the most important components of a prosthetic leg, providing the foundation for comfortable, stable, and confident movement. Designed to replicate the function of a natural foot, it helps absorb impact, support your body weight, adapt to different terrains, and promote a smooth, natural walking pattern.

Every time your foot makes contact with the ground, it absorbs shock and helps transfer energy through your body. A well-designed prosthetic foot reduces the impact on your residual limb and joints while improving balance, stability, and walking efficiency. Many modern prosthetic feet also store and release energy during each step, making walking feel more natural and less physically demanding.

There are many different prosthetic foot designs available to suit a wide range of lifestyles and mobility goals. Whether your priority is everyday walking, work, hiking, running, sports, or navigating uneven terrain, your prosthetist will recommend a foot that matches your activity level, weight, rehabilitation goals, and individual needs.

Choosing the right prosthetic foot can significantly improve comfort, confidence, and quality of life by helping you move more naturally and participate in the activities that matter most.

Click here to explore our prosthetic feet.

Adapters 

An adapter is any prosthetic component that links the main components, such as the liner, knee and foot together. Adapters can vary from components such as a simple tube (which is called a pylon) to an expulsion valve in a vacuum system. 

Cosmesis 

A cosmesis is a lifelike covering made from a material such as silicone or PVC. Its purpose is to mimic the appearance of a biological limb, and may be complete with freckles, veins, hair or even tattoos. A cosmesis can also protect the prosthetic components from the elements. 

Some types of cosmeses are ready-made, but for a truly realistic appearance a cosmesis must be custom designed and manufactured by a prosthetist who specializes in this aspect of prosthetics.  

The use of a cosmesis is a personal choice. You will get to weigh the benefits of appearance of a cosmesis against the extra costs and potential impacts on functionality when deciding whether to wear one or not. 

Specialized Components 

Prosthetic technology has come a long way toward helping people who have had an amputation enjoy greater mobility. Some of the most advanced prosthetics, like Bionic prosthetics, have on-board microprocessor computers and artificial intelligence (AI) that automatically adjust to changes in terrain, and adapts real-time to your walking speed and style. 

While the same prosthesis can be used for a range of activities, such as hiking, jogging, and showering, other activities, such as sprinting, long-distance running and swimming, require a specialized prosthesis. If you plan to go jogging, running or sprinting regularly, it’s better to use components made specifically for that, such as the Cheetah blade. 

One recent innovation from Össur is a unique crossover foot prosthesis inspired by the original Cheetah design. Although primarily designed for everyday use, the Cheetah Xplore allows the user to engage in various sports and activities without changing the prosthesis.  

By openly discussing your ambitions and lifestyle requirements with your prosthetist while staying informed about new technology, you can be sure that you are getting the benefits of the latest technology. 

We hope these descriptions are a helpful start to understanding this new part of your daily life. Remember to always ask the specialists you are working with about your new prosthetic leg and how it works. It is a great way to empower yourself as you move into your new life with a prosthetic leg.