Microprocessor Knee Joints
Sensor- and software-supported knee joints; how they work and how they are assessed.
What is a microprocessor knee prosthesis?
A microprocessor knee prosthesis is a lower limb prosthetic component used for limb loss at the knee level that contains sensors, software and a small processor. This system continuously detects which phase the leg is in during walking and adjusts the resistance provided by the knee in real time. As a result, walking may become more stable and more natural compared with conventional mechanical knees.
Microprocessor knees aim to make it easier for the prosthesis user to walk at different speeds, descend ramps and stairs and move on uneven ground. The knee adapts its settings to the user's individual walking pattern and changes the support accordingly when the speed changes.
This page aims to provide an informative overview of how microprocessor knee prostheses work, their main components, how they differ from mechanical knees and their general features. Which prosthetic solution is suitable for a person depends on the level of amputation, the condition of the residual limb and the general physical condition, and this assessment is made by the relevant health and prosthetics professionals.
Subtopics and knee systems
Detailed topics on microprocessor-controlled knees and types of knee systems.
Mechanical vs. Microprocessor
A comparison of the two system approaches.
Learn moreStumble Control
Balance support during sudden load changes.
Learn moreIntuitive Standing Support
Safe behavior during the stance phase.
Learn moreWater and Dust Resistance
Environmental durability and use.
Learn moreWalking Modes
Modes that can be programmed according to activity.
Learn moreHigh-Activity Knee
A knee system for more active use.
Learn moreDaily Activity Knee
A knee focused on safety and stability.
Learn moreHydraulic (Mechanical) Knee
A mechanical knee system without a microprocessor.
Learn moreMicroprocessor Knee for Children
A knee intended for pediatric use.
Learn moreControl App for the Knee
An app that helps with adjustment and monitoring.
Learn moreThe gait cycle: stance and swing phase
All prosthetic knees are designed to imitate the two main phases of natural walking, that is, the gait cycle. A microprocessor knee detects these two phases through its sensors and tries to provide the appropriate resistance for each phase.
- Stance phase: The foot is in contact with the ground. The leg remains slightly bent; the knee provides enough resistance to carry the body weight while also acting like a shock absorber.
- Swing phase: The foot is in the air and swings forward. The knee bends further, allowing the foot to move on to the next step without catching on the ground.
The difference between mechanical knees and microprocessor knees
Mechanical knee prostheses are usually controlled by a mechanical lock, friction, or pneumatic or hydraulic fluids. In these systems, mostly only the body weight activates the stance control mechanism; in some cases this can lead to a less natural gait. In microprocessor knees, on the other hand, sensors, software and a built-in processor adjust the fluid-based resistance to the user's own walking pattern. As a result, walking at different speeds and descending ramps and stairs generally become safer and less tiring. The overall aim is to provide a more stable, more natural and more energy-efficient gait.
Main components and working principle
A microprocessor knee functions through several components working together. Sensors collect data from every phase of walking; the processor evaluates this data; and a hydraulic or similar resistance unit adjusts the bending and extension behavior of the knee in real time.
- Sensors: Determine the gait phase by continuously measuring data such as angle, speed and load.
- Processor and software: Evaluate the collected data and decide how the knee should behave.
- Resistance unit (hydraulic/pneumatic): Adjusts the resistance to bending and extension according to the processor's decision.
- Power source: A rechargeable battery is provided for the electronic components to operate.
- Programming: The prosthetist adjusts the knee to the person's walking pattern; some systems also adapt in real time during walking.
Notable general features
Microprocessor knees may offer various functions aimed at increasing safety and comfort in everyday life. Which of these features a device has varies by model.
- Gait adaptation: Even if the surface, speed or the weight being carried changes, the knee tries to adapt to walking using sensor data.
- Stumble recovery support: When the system detects a possible stumble, it may help maintain balance by increasing resistance.
- Standing support: Stance control functions that make it easier to stand in a balanced way even on sloped or uneven ground.
- Water and dust resistance: The durability of devices is expressed by the international IP protection rating; the level of protection differs by model.
- Activity modes: Additional movement settings that can be programmed by the prosthetist for specific sports or repetitive tasks.
- Bilateral use: Functions intended to support a more symmetrical and safer gait in people with limb loss in both legs.
Activity levels and suitability assessment
A criterion frequently used in choosing a prosthesis is the person's activity (mobility) level. This level is usually expressed as a value between 1 and 4 and reflects the person's general physical condition, walking capacity and potential to benefit from different prosthetic options. The assessment is made by the relevant prosthetics and health professionals.
- Level 1: The prosthesis is usually used for transfers or for slow, short-duration movement on level ground; walking distance is markedly limited.
- Level 2: The user can walk slowly and overcome low barriers such as curbs, a single step or slight unevenness; distance is still limited.
- Level 3: Walking at moderate to high speeds, changing speed and overcoming most natural barriers are possible.
- Level 4: The person can walk outdoors without restrictions on duration or distance; high mechanical loads may occur together with high functional demands.
Points to consider in care and use
Because microprocessor knees contain electronic components, regular maintenance and correct use are important for the functionality of the device. Since each device's resistance to water, dust and external factors differs, the conditions of use should be determined according to the device's protection rating.
- The battery needs to be charged regularly in accordance with the manufacturer's instructions.
- Exposure of the device to water or moisture is appropriate only to the extent permitted by the protection rating of the relevant model; salt or chlorinated water may not be suitable for all models.
- Periodic checks and reprogramming when necessary are recommended so that the settings remain suited to the person's gait.
- Physiotherapy support plays an important role in safe and effective use during the adaptation process with a new prosthesis.
- In case of any malfunction, unusual noise or behavior, the device needs to be evaluated by the relevant specialists.
Application process
Physician's prescription / report
The process starts with a prescription or medical report issued by a specialist physician. No application is made without a prescription or report.
Assessment and measurement
The person's condition is assessed; measurements are taken for custom-made production and a service plan is prepared.
Production and fitting
The custom-made prosthesis or orthosis is produced; fit and alignment are adjusted during the fitting stage.
Application and user training
The device is applied; use, cleaning and care are explained.
Follow-up
Follow-up is provided for check-ups, maintenance and repair after the application.
Related informational content
Microprocessor Knee Joints: How Do They Work?
ReadMechanical or Microprocessor? Differences Between Prosthetic Knee Joints
Read
Information on Microprocessor Knee Joints for Children
ReadApplications are carried out in line with a specialist physician's prescription or medical report, at our licensed center addresses. This content is for information only; please consult your physician for diagnosis and treatment.