10 Questions You Should to Know about Lightweight Knee Joint for Prosthetic Leg

Individuals facing amputation above the knee can discover a renewed sense of mobility and independence through above-the-knee prosthetics. These prosthetic legs are meticulously designed to replicate the function, and often the appearance, of a real leg. While the benefits of above-the-knee prosthetics can greatly enhance the quality of life, it's important to recognize and address potential problems associated with this type of prosthetic solution. With years of experience in the field, our team at PrimeCare Orthotics & Prosthetics is uniquely qualified and ready to help answer your questions about this topic.

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What Is Above-Knee Amputation (AKA)?

Above-knee amputation is a surgical procedure that involves the removal of the leg above the knee joint. This type of knee amputation is typically the result of critical health issues such as peripheral vascular disease, which restricts blood flow, leading to the death of tissues. Other causes may include unmanageable foot or leg ulcers, particularly in diabetic patients, or severe trauma resulting from accidents. We understand that the decision to proceed with an above-knee amputation is never taken lightly and is usually a last resort when other medical interventions have failed to resolve the underlying problems.

Preparing for an Above-the-Knee Amputation

Preparing for a lower extremity amputation requires thoughtful consideration and careful planning. In most cases, you'll work closely with a specialized vascular or orthopedic surgeon who will guide you through the process. Here are some steps you may need to take:

• Consultation: Have a detailed conversation with your surgeon about the procedure, risks, and outcomes including rehabilitation and prosthetic training.
• Preoperative Instructions: Once surgery is scheduled, your provider may instruct you not to eat or drink after midnight before surgery. They'll also guide you on which medicines to take or avoid.
• Antibiotics: You may be given an antibiotic through your IV to prevent infection. Be sure to inform your healthcare provider about any allergies to antibiotics.
• Imaging and Testing: In addition to doctor-prescribed antibiotics, an angiogram might be needed to check blood flow, involving a catheter, contrast liquid, and X-rays. Let your provider know if you have allergies to contrast liquid. Oxygen level tests in your leg might also be conducted to decide the amputation site.
• Physical Therapy: Preoperative physical therapy might be recommended to strengthen muscles.
• Mental Preparation: Consider counseling or support groups to help mentally prepare for the life changes.
• Home Adjustments: Make necessary home modifications to accommodate mobility changes.

After an Above-the-Knee Amputation Surgery

Patients may experience a variety of physical sensations and changes as they adapt to life without the limb. These might include phantom limb pain, where the individual continues to feel the part of the leg that has been amputated. Phantom pain is normal and is often successfully managed with prescription pain medicine.

• Initial post-surgery care includes the placement of drains to remove fluid from around the incision and respiratory exercises to reduce the risk of lung infections. Patients are encouraged to take deep breaths and cough frequently, often using an incentive spirometer for help.
• Physical care for the remaining limb is critical. Be sure to change positions regularly to prevent complications such as pneumonia or skin pressure sores and specific guidelines for the first 24 hours to reduce swelling. You'll also want to do strengthening exercises for the hip muscles and residual limb, paying special attention to limb positioning to prevent hip tightening.
• Wrapping the residual limb with an elastic bandage helps control swelling and forms the limb into a shape suitable for fitting a prosthesis. This wrapping usually starts within days of surgery and continues until healing is well underway.

As the healing process continues, the focus gradually shifts to selecting the appropriate prosthesis for the remaining limb. This involves collaboration between healthcare providers, prosthetic specialists, and the patient, ensuring the prosthesis fits well and enhances mobility. The goal is to integrate the prosthesis seamlessly into daily life, allowing for improved function and independence.

What Are the Different Above-the-Knee Prosthetic Types?

You’re likely wondering “What kind of prosthetic leg do I need for an amputee above the knee?” There are different types of above-the-knee prosthetics to consider, and the PrimeCare Orthotics & Prosthetics team works with the following technologies:

• C-Leg, Genium, X3 knees, Power/Rheo knees
• Propio Foot
• i-Limb
• I-digits Quantum
• Be-Bionic Hand

Your doctor will work with you on choosing the best type of prosthetic for your needs.

What Type of Prosthesis Replaces the Leg Above the Knee?

Those who need above-knee prosthetic legs (also referred to as a transfemoral prosthesis) usually consist of a custom-made socket, a knee, a pylon, a foot, and some way to suspend the prosthesis from the body. It’s common for patients to be fitted for a prosthetic within a few days of surgery.

Immediately following the procedure, you’ll receive an Immediate Post-Operative Prosthesis (IPOP) to help reduce swelling, protect wounds, and speed up the overall healing process. In some cases, you might receive an AK shrinker, a device that helps to shape your limb for the prosthetic and desensitizes the limb to make the prosthetic more comfortable.

Don't rush the process of getting a long-term prosthesis. It’s important to get both the right type of prosthesis and the right fit. During the process, you will:

• Receive a liner that cushions your limb
• Receive a cast made out of your limb
• Try a diagnostic socket to ensure alignment for the final prosthesis
• Receive subsequent diagnostic sockets to achieve the right fit
• Get a final version of the socket to start gait training
• Finally, select the knee and prosthesis that's best for you

How Does an Above-Knee Prosthetic Work?

There are different parts of an above-knee prosthesis — a socket, knee joint, ankle joint, and foot components. As we mentioned above, you’ll first receive a temporary prosthesis while your residual limb heals, shrinks, and changes shape over a few months of healing. Your prosthesis will be modified to fit your residual limb.

Here's additional information on how the parts of a prosthesis work together:

• The prosthetic leg is made from durable yet lightweight materials. The leg may or may not include functional knee and ankle joints depending on where the amputation occurs.
• The socket is made from an exact mold of your residual limb and it’s designed to fit snugly. The socket helps to attach the prosthetic to your body.
• The suspension system, or how the prosthesis stays attached to the limb, may include sleeve suction, distal locking, or vacuum suspension.

During the rehabilitation process, you’ll begin to learn to function first with a wheelchair and walking assistance devices such as crutches or a walker. Before you learn how to walk with an above-knee prosthetic, you’ll work closely with your physical therapist to learn the necessary skills to use your prosthetic limb. Physical therapists will also provide you with information on how to care for it, including skin checks, hygiene, contracture prevention, exercise, and positioning.

Everyday Routine with an Above-Knee Amputation

Once you have your prosthesis, you’ll need to invest time into ongoing therapy and at-home exercises under the guidance of your doctor. Through time and consistent effort, you can learn balance and coordination. Try to be as patient as possible as it’s not uncommon for rehab to last up to 1 year. You’ll also want to check the remaining limb daily for any irritation, skin breaks, or redness.

Just because you have a prosthetic, it doesn’t mean that you can have an enjoyable and fruitful life. At home, make sure to discuss with your doctor what you can do. When you get the okay, you’ll be able to wash the remaining limb with soap and water. It’s also possible that you’ll be able to drive depending on your specifics. Some people can return to work as soon as 4-8 weeks following surgery although it could take longer.

How Do People with Above-Knee Prosthetics Walk?

As above-knee amputations make it harder to bear weight, the risk of falling is higher. First, those with an above-knee prosthetic leg will use a wheelchair until the risk of falling is low. During this time, you’ll use rehabilitation and physical therapy to build strength. You’ll also be fitted with short prosthetic training feet that help to re-learn balance. Gradually, you'll increase the height of the prosthetic leg to build the strength needed for a full-length prosthetic. Over time and with practice, amputees will be able to walk without the assistance of any devices. In fact, one of our success stories at PrimeCare, Ralph, tells us that one of his biggest accomplishments is walking up and down the stairs without pain after being fitted for his prosthetic.

How Far Can You Walk with a Prosthetic Leg?

The distance that you can walk depends on your injury and overall healing process. Some people can only walk a short distance before getting too tired or feeling too much pain while others can get around as they did before surgery.

How to Play Sports with an Above-Knee Limb

Different sports have unique requirements. Popular sports for those who have prosthetic legs include cycling and swimming. These are popular as they are non-weight-bearing sports. Other people with prosthetic legs may be able to walk, run, dance, or even garden or practice yoga. Think outside of the standard sports and consider trying something you haven’t tried before.

Safely Falling with an Above-the-Knee Amputee

Learning how to fall properly can help keep those with a prosthetic safe. Your physical therapist will practice falling with you. If you're falling, make sure to immediately release any assistive devices you’re using and allow the body to be flexible. If possible, absorb the impact with your hands by using slightly bent elbows and immediately roll to the side to minimize impact. Avoid hitting your head by tucking your chin to your chest.

How to Sit with Prosthetics

When sitting, keep your shoulders back with your pelvis beneath you. Your limb should be aimed at the floor and hang close to your other leg.

3 Tips for Above-the-Knee Amputees to Feel Comfortable

1. Start Slowly: Take your time and be patient when you’re learning to walk with your new prosthetic leg. Parallel bars can help keep you secure and build your confidence without the risk of falling.
2. Shift Your Weight: As you take steps, it becomes an unconscious movement for you to shift weight between your legs. Make sure to practice this shift in weight when you’re learning to walk.
3. Build Confidence Through Repetition: Once you’re comfortable using the basic walking mechanics, practice them repeatedly to build your confidence. The more confident you feel, the better you’ll navigate the world with your artificial leg.

Potential Above-the-Knee Amputation Complications

We’ve outlined some common above-the-knee amputation complications.

What Are the Negative Effects of Prosthetics?

It can be physically and mentally challenging to adjust to a prosthetic leg. Here are some common obstacles:

• Excessive sweating may affect how the prosthesis fits, resulting in skin issues
• Changing residual limb shape that often occurs in the first year after amputation
• Residual limb weakness makes it difficult to use the prosthesis for a long period of time
• Phantom limb pain

Does Leg Amputation Shorten Life Expectancy?

There are prolonged physical and psychological stressors that can impact the life expectancy of lower limb amputees. For example, there's an increased morbidity and mortality rate from cardiovascular disease. Stress, insulin resistance, and behaviors including alcohol use, smoking, and physical inactivity are all prevalent in lower limb amputees. Other health complications include infection, excessive bleeding, muscle shortening, and pulmonary embolisms.

How Long Is Rehab After Leg Amputation?

Every patient is different, however, the rehabilitation process can last as long as one year.

PrimeCare Orthotics & Prosthetics Can Help!

There are many prosthetic leg options to choose from, and the best fit will be dictated by an individual’s level of injury, physical factors, complications, as well as their lifestyle and vocational or recreational goals.

Every amputation is different, and it is critical that persons who have sustained an amputation work with a certified prosthetist and physiotherapist to determine which kind of prosthesis will be the best option for them.

In this article, we will highlight prosthetic leg options and physiotherapy for through-knee or above knee amputation.

Table of Contents:

• What is a prosthetic leg?
• Common causes and complications of amputations
• Types of knee prostheses
• Mechanical knees
• Single axis knees
• Polycentric knees
• Manual locking knees
• Weight activated stance control knees
• Pneumatic or Hydraulic Knees
• Computerized knees
• Physiotherapy after leg amputation
• Conclusion

What is a Prosthetic Leg?

Prosthetic legs allow an individual who has sustained an amputation to walk with a more normal and energy efficient gait pattern and will often allow them to walk without the need for assistive devices such as crutches or walkers. In addition to enabling a more normal gait pattern, they allow the user to accommodate for sitting/standing, stairs/ramps as well as uneven terrain and different walking speeds.

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A prosthetic leg includes several components including the socket, which is molded to the individual’s residual limb, the suspension system, which is how the prosthesis stays attached to the individual, and the prosthetic leg itself, which includes different options for knee and ankle joints.

Individuals can be fitted for a prosthesis once the wound from the amputation is stable and well-healed, which can be within a few weeks after the surgery. This may be delayed if they have complications related to the amputation.

After an above-knee or through-knee amputation, the residual limb shrinks, as the individual loses muscle mass in their thigh. Users will need to be fitted for multiple sockets over time to accommodate for the decreasing size of their residual limb.

Common Causes and Complications of Amputations

Amputation refers to the removal of a limb due to injury, disease, or surgery. It can be utilized as a surgical procedure to manage discomfort or a disease condition in the affected limb. Individuals can also undergo traumatic amputations resulting from motor vehicle accidents or workplace accidents.

There are several complications related to amputation such as infection, phantom limb pain (residual limb pain), slow wound healing, vascular issues and necrosis, neuromas, edema, and skin breakdown. Phantom pain is a common occurrence after an amputation and is perceived in the limb that has been removed from the body. It is typically characterized as a sharp or burning pain that occurs due to a miscommunication of nerve signals from the brain to the spinal cord.

Types of Knee Prostheses

Prosthetic knees allow a person who has sustained an amputation at or above the knee to regain use of the knee and ankle joints and participate more easily in their daily activities.

Prosthetic knees are divided into two categories, mechanical or computerized. Mechanical knees are further divided into single-axis, multi-axis, and polycentric knees. Each prosthesis has its own unique features which are chosen based on the user’s requirements.

Mechanical Knees

Single-Axis Knees Mechanism and Indications

This is the simplest type of prosthetic knee joint that allows for rotation around a single axis during flexion and extension of the knee. Individuals who use this type of knee require good muscle strength, as this type of prosthesis can be difficult to control. These are sometimes recommended when there are limited economic resources, as it is the most cost-effective option.

Advantages:

• This is a very simplistic design, durable, as well as light weight, which can be helpful for new amputees, who are just learning to walk.
• Most cost effective

Disadvantages: 

• Due to this simplistic design, the user has to generate significant muscle power to keep the knee stable while standing and walking.
• Creates an unnatural gait pattern due to the simplicity of the single-axis design
• Can be difficult to control the locking and unlocking during gait, putting the user at higher risk for falls and injuries.

Polycentric Knees Mechanism and Indications

Unlike a single-axis knee, a polycentric knee allows multiple points of rotation around several axes. Polycentric joints can have either 4 or 7 bars, meaning that you can either have 4 points of rotation or 7 points of rotation. This type of joint provides good stability when there is involuntary flexion during the heel strike phase of walking because the center of rotation is located more proximally and posterior when the knee is fully extended. This knee is typically recommended for active people, or people who are more likely to walk independently, without a gait aid.

Advantages:

• Can be very stable in stance phase
• Allows the user to sit down with a bent knee
• Due to the multiple axes and the center of rotation, the prosthetic length “shortens” at the start of the swing phase of walking to allow for foot clearance
• Lighter than computerized knees
• Less expensive than computerized knees

      Disadvantages: 

• Much heavier than a single-axis joint prosthesis
• Greater energy requirement of muscles during walking to maintain gait efficiency and balance.

Manual Locking Knees Mechanism and Indications

This type of joint locks while the user is weight-bearing on it. They will need to manually disengage the lock to be able to sit down.

      Advantages:

• Very stable
• Allows for an automatic lock in weight-bearing, with the additional option to manually lock the knee. This is especially important for people with less muscle control and balance, or who need more security while walking on uneven terrain.

      Disadvantages:

• The user will need to swing the leg out or hike the hip to allow for adequate foot clearance during gait. This is an unnatural gait pattern, which can lead to further issues in the future in surrounding muscles and joints.
• Need to manually unlock the knee to sit with a bent knee

Weight Activated Stance Control (Safety) Knees Mechanism and Indications

This knee provides a constant friction force while weight is on the limb. This helps to prevent it from buckling when standing on that leg, while still allowing it to swing freely when unweighted.

      Advantages:

• This is a very stable knee that is commonly prescribed when individuals first start using a prosthesis, and in older individuals and the less active community.
• This is also for people who can exert some control over their knee, but who fatigue quickly after a few steps, or people who forget that they cannot put weight onto a bent knee while using their prosthesis.

      Disadvantages:

• With this prosthesis you are unable to get into a sitting position without taking all your weight off the leg.
• The individual has to take all of the weight off their affected side to allow it to swing resulting in a less efficient gait pattern
• Due to the constant friction in the knee, the individual will walk slower, with smaller steps.

Pneumatic or Hydraulic Knees Mechanism and Indications

Pneumatic/hydraulic components (pistons with cylinders containing air or fluid) can be added to either single-axis or polycentric mechanical knees, as well as computerized knees. This is to help increase mobility and control with the leg and allow the user to vary speeds. When walking faster it will limit the air flow and fluid to reduce the flexion of the knee to allow a faster walking pace. The opposite will happen with a slower gait. Typically, hydraulic knees work well for more active individuals.

      Advantages:

• Allows the individual to walk more comfortably and with a more natural gait pattern.
• This type of knee also allows the individual to walk up and down the stairs with a reciprocal gait pattern, due to the resistance provided during flexion while there is weight on the leg.
• This is both less expensive and lighter than computerized knees.

Disadvantages:

• Hydraulic knees are often more expensive and heavier than pneumatic knees, they also need more maintenance.
• Cost is higher than mechanical knees.

Computerized Knees

Mechanism and Indications

These knees have microprocessors to allow feedback from within the knee or foot joint. Information from the sensors adjusts the range and speed of knee flexion and extension, according to the user’s requirements. Knee extension is powered, and resistance is provided through knee flexion, allowing the individual to more easily get in and out of a sitting position, and navigate stairs using a reciprocal gait pattern.  It also allows for a symmetrical weight distribution and a natural gait pattern.

      Advantages:

• These are much more advanced, which allows the gait to be more natural as well as allowing the leg to adjust to different speeds. Some offer stumble control, which will automatically put the leg into a position to prevent you from falling. This type of prosthesis allows the user to adjust to changes in speed, environment changes and specific situations. These also have different programmable modes for when you are doing different activities (i.e. cycling)
• More efficient gait pattern with less energy expenditure during gait
• Allows the user to navigate stairs using a reciprocal gait pattern

     Disadvantages:

• These are very expensive and need to be charged regularly.
• Heavier than the other options and can also be damaged by different environmental conditions.
• Can be more difficult to cover or wear certain types of clothing overtop
• Learning curve when first starting to use this type of device
• Regular maintenance required

Physiotherapy After Leg Amputation

The nature of rehabilitation after a leg amputation at or above the knee will depend on the client’s goals and physical presentation but will often include:

• Gait assessment and prosthesis training
• Gait aid training
• Transfer training
• Static and dynamic balance training
• Strengthening the hip muscles of the residual limb, as well the muscles of the sound leg, and core.
• Desensitization techniques / mirror box therapy
• Manual therapy – to normalize muscle tension and joint mobility
• Edema management
• Education on activity modification and return to recreational activities
• Collaboration with the prosthetist on adjustments to the prosthesis

Conclusions

When an individual has undergone an amputation at or above the knee, learning to use a prosthetic leg is often a crucial step in the rehabilitation process. A well-fitting prosthesis can help individuals regain mobility and return to their daily activities. This allows the freedom and independence to get back to doing the activities that are important to them.

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