For people with an above knee amputation, choosing the right prosthetic knee can have a significant impact on mobility, confidence and everyday function.
Two of the main options are mechanical knees and microprocessor prosthetic knees. Both are designed to replace some of the movement and stability provided by the natural knee joint, but they control movement in different ways.
The most appropriate choice depends on factors such as mobility level, lifestyle, balance, walking environment and rehabilitation goals. The knee is also only one component of a complete prosthetic system, so socket fit, alignment and the prosthetic foot all need to work together.
At Head to Foot Orthotics and Prosthetics, our prosthetists support patients across Croydon, Alexandra, Ballarat, Berwick and Dandenong with personalised prosthetic assessment, fitting and ongoing care.
What Is a Prosthetic Knee?
A prosthetic knee is a component used in an above knee prosthesis, also known as a transfemoral prosthesis.
Because an above knee amputation involves the loss of the natural knee joint, the prosthetic system needs to provide stability and controlled movement during standing and walking.
Depending on the individual and the knee system being used, a prosthetic knee may help with:
- Stability while standing
- Controlled bending during walking
- Changes in walking speed
- Movement across different surfaces
- Sitting down and standing up
- Navigating slopes, ramps and other everyday environments
Different types of prosthetic knees achieve this control in different ways.
What Is a Mechanical Prosthetic Knee?
A mechanical knee uses physical mechanisms to control how the knee bends and extends.
Depending on the design, this may involve:
- Simple hinges
- Friction systems
- Hydraulic resistance
- Pneumatic resistance
- Locking mechanisms
Unlike a microprocessor knee, a traditional mechanical knee does not use an onboard computer to continuously monitor movement and electronically adjust resistance.
However, there is considerable variation between mechanical knees. Some are deliberately simple and highly stable, while more sophisticated hydraulic and pneumatic systems can provide smoother and more responsive movement.
What Are the Benefits of Mechanical Knees?
Mechanical knees can be an effective option for many prosthetic users and continue to play an important role in modern prosthetic care.
Potential benefits can include:
- Reliable operation
- Relatively simple maintenance
- Good durability
- Lower weight with some designs
- No regular battery charging
- Lower cost than many microprocessor systems
- Stable options for people who require additional support
For some people, a mechanical knee provides the right balance of stability, mobility and simplicity for everyday activities.
What Are the Limitations of Mechanical Knees?
Mechanical knees generally require the user to control more of the prosthesis through their body movement, strength and walking technique.
Depending on the particular knee and the needs of the user, limitations may include:
- Less automatic adjustment when walking speed changes
- Greater concentration when navigating uneven surfaces
- Less adaptability on ramps and slopes
- Less sophisticated stumble recovery
- Greater reliance on hip strength, balance and gait technique
These factors do not mean that mechanical knees are inferior. The important consideration is whether the characteristics of the knee match the individual’s mobility requirements and goals.
What Is a Microprocessor Prosthetic Knee?
A microprocessor prosthetic knee, commonly referred to as an MPK, uses electronic sensors and an onboard microprocessor to monitor aspects of the user’s movement.
The system can make rapid adjustments to the resistance of the knee based on information such as movement, loading and the position of the prosthesis during different phases of walking.
Depending on the particular system, this can allow the knee to respond dynamically when the user changes speed or encounters different walking conditions.
Microprocessor knees are one example of how advances in prosthetic technology are providing more options for people living with limb loss.
What Are the Benefits of Microprocessor Knees?
Microprocessor-controlled systems are designed to provide responsive control and stability during everyday movement.
Depending on the individual and the device, potential benefits may include:
- Improved control during walking
- Smoother transitions between different walking speeds
- Increased stability in changing environments
- Improved control when walking down ramps or slopes
- More responsive stumble recovery
- More natural movement patterns for some users
- Reduced need to consciously control certain aspects of knee movement
For an appropriate prosthetic user, these features may make it easier to navigate a wider variety of everyday environments.
What Are the Limitations of Microprocessor Knees?
While microprocessor knees offer advanced functionality, they are more complex than purely mechanical systems and are not automatically the best choice for every person.
Considerations can include:
- Higher cost
- Battery charging requirements
- More specialised servicing
- Additional component weight with some models
- Different levels of water resistance depending on the device
- Funding and eligibility requirements
Lifestyle is important as well. A person who spends significant time around water, dust or demanding work environments may have different priorities from someone whose primary goal is community mobility across varied terrain.
Mechanical Knees vs Microprocessor Prosthetic Knees: What’s the Difference?
The fundamental difference between the two systems is how they control movement.
| Feature | Mechanical Knee | Microprocessor Knee |
|---|---|---|
| Movement control | Mechanical resistance | Electronically controlled resistance |
| Electronic sensors | Generally no | Yes |
| Automatic adaptation | Limited and design-dependent | Greater real-time adaptation |
| Battery required | Generally no | Yes |
| Walking speed adjustment | Depends on knee design | Can automatically respond to changes |
| Uneven terrain support | Varies between designs | Often more responsive |
| Maintenance | Generally simpler | More specialised |
| Cost | Usually lower | Usually higher |
There is significant variation within both categories, so these differences should be treated as a general guide rather than a comparison of every available prosthetic knee.
Which Prosthetic Knee Is Best?
There isn’t one prosthetic knee that is best for every person.
A prosthetist will consider factors such as:
- Level of amputation
- Condition of the residual limb
- Strength and balance
- Current walking ability
- Daily activity level
- Work requirements
- Home environment
- Recreational activities
- Rehabilitation goals
- Previous experience with prosthetic limbs
Someone who regularly walks across changing terrain, for example, may have very different requirements from someone whose priority is stable and predictable movement around their home.
If you’re considering your prosthetic options, our guide to choosing the right prosthetist in Melbourne also explains some of the factors to consider when choosing a prosthetic care provider.
Mobility Level and Prosthetic Knee Selection
Activity and mobility levels are important considerations when selecting prosthetic components.
Some prosthetic users may prioritise:
- Maximum stability
- Simple operation
- Low maintenance
- Predictable movement
Others may require:
- Variable walking speeds
- Greater terrain adaptability
- Increased community mobility
- More responsive control on ramps and slopes
- Support for an active lifestyle
The goal is not necessarily to select the prosthetic knee with the most technology. It is to find a system that supports the activities the individual actually wants and needs to perform.
Rehabilitation With a Prosthetic Knee
Regardless of whether a mechanical or microprocessor knee is selected, rehabilitation can play an important role in learning to use an above knee prosthesis.
This may include:
- Strengthening the hips and core
- Balance exercises
- Gait training
- Learning safe weight transfer
- Practising changes in walking speed
- Navigating ramps, steps and uneven surfaces
- Developing confidence with the prosthesis
Our guide to life after amputation provides more information about recovery, rehabilitation and the process of adapting to a prosthesis following limb loss.
Why Prosthetic Fitting and Alignment Matter
The knee component is only one part of an above knee prosthesis.
A complete prosthetic system may include:
- A custom prosthetic socket
- Suspension system
- Prosthetic knee
- Structural components
- Prosthetic foot
These components need to work together.
Socket comfort, alignment and the relationship between the knee and foot can all influence how the prosthesis feels and functions. Even an advanced microprocessor knee cannot compensate for every issue associated with an unsuitable socket or poor alignment.
Regular reviews with a prosthetist are therefore an important part of ongoing prosthetic care.
Can You Change From a Mechanical Knee to a Microprocessor Knee?
In some circumstances, a prosthetic user may move from one type of knee to another over time.
Reasons for considering a different prosthetic knee might include:
- Improved mobility
- Progress through rehabilitation
- Changes in work or lifestyle
- Different activity goals
- Changes in physical ability
- Funding becoming available
- Changes in prosthetic technology
Changing to a different knee isn’t automatically an upgrade. A prosthetist can assess whether another system is appropriate and whether it is likely to provide meaningful benefits for the individual.
Prosthetic Knee Assessment and Care Across Victoria
Head to Foot Orthotics and Prosthetics provides prosthetic services across Victoria, including assessment, fitting and ongoing prosthetic care.
Our clinic locations include:
- Croydon
- Alexandra
- Ballarat
- Berwick
- Dandenong
Our prosthetists work with people experiencing limb loss to understand their mobility needs, lifestyle and rehabilitation goals before considering appropriate prosthetic components and solutions.
Frequently Asked Questions
Are microprocessor knees better than mechanical knees?
Not necessarily. Microprocessor knees provide electronic control and real-time adjustment, but this does not mean they are the most appropriate choice for every prosthetic user. Mobility, lifestyle, physical ability, environment and individual goals all need to be considered.
Do microprocessor prosthetic knees need charging?
Yes. Microprocessor knees contain electronic components and batteries and generally require regular charging. Charging requirements vary between different knee systems.
Are mechanical prosthetic knees safe?
Mechanical prosthetic knees are widely used and can provide effective stability and mobility when the knee is appropriately prescribed, fitted and aligned for the individual.
Can you walk on uneven ground with a microprocessor knee?
Many microprocessor knee systems are designed to respond to changing walking conditions and may provide additional control across varied terrain. Capabilities differ between individual devices, and users still need appropriate training and rehabilitation.
How do I know which prosthetic knee is right for me?
A prosthetist can assess factors including your level of amputation, strength, balance, current mobility, lifestyle, environment and rehabilitation goals before discussing appropriate prosthetic knee options.
Can I try different prosthetic knees?
Depending on the individual’s circumstances, available components and funding arrangements, it may be possible to assess or trial different prosthetic knee options. Your prosthetist can explain which systems may be appropriate for your needs.
