Össur Power Knee: the active, motor-powered bionic knee
Össur’s Power Knee is a motor-powered microprocessor knee: it does not just control movement, it adds power when you rise from a chair, walk and climb stairs.
Bionic technology · Össur
Össur Rheo Knee: the knee that learns how you walk
Össur’s Rheo Knee is a microprocessor knee that “learns” the way you move and adapts automatically, for comfortable walking at any speed, on slopes and on steps.
- Learns and adapts to the way you walk
- Magnetorheological fluid for instant response
- Comfortable walking at any speed, on any ground
- Resistant to rain and moisture
- Össur Logic app with exercise programme
Össur’s Rheo Knee is a microprocessor knee for people with an above-knee amputation. Its great strength is personalised function: the knee recognises the way you walk, “learns” from your habits and automatically adapts its behaviour, so that you can walk naturally and without effort, even on uneven ground. At Hlamidis Orthopaedic Center in Thessaloniki we fit the Rheo Knee as part of a complete above-knee (transfemoral) prosthesis.
How the Rheo Knee works
At the heart of the Rheo Knee is a magnetorheological fluid. This is a fluid whose “thickness” (viscosity) changes within fractions of a second when a magnetic field is applied. In this way the knee works like an electronic brake: sensors continuously record your movement and the microprocessor adjusts the resistance according to your speed, the ground and the activity. The result is a knee that supports you when needed and lets the leg move freely when it is not.
What the Rheo Knee offers you
- Natural walking at any speed: the knee follows your rhythm, whether you walk slowly or in a hurry.
- Adapting to the ground: slopes, steps, tight spaces and uneven surfaces can be handled with more confidence.
- Enhanced stability control: designed to help you feel more stable, especially at the start of fitting and training.
- Weather-resistant: it can be used in wet conditions and in the rain, but it is not intended for immersion in water.
The Össur Logic app
With the Össur Logic app, the prosthetist can easily set up the knee, tailor how it works to each user and access activity reports. You can quickly check the battery charge and your step count, and follow a specially designed home exercise programme at your own pace to improve your gait and your confidence.
Who the Rheo Knee is for
According to Össur, the Rheo Knee is intended for users with activity levels (mobility grades) K2 to K3. In simple terms: from people who walk outside the home, managing small obstacles such as kerbs and steps, to those who get around town every day at different speeds. For users with very high demands, such as intensive sport, we consider other versions or systems. It is fitted for above-knee amputation and knee disarticulation. The final choice is made after an assessment and together with your doctor.
Fitting and training in Thessaloniki
The process starts with an assessment of your residual limb, your strength and your goals. We then make a test socket tailored to you so that we can fine-tune the fit, followed by the definitive socket. We set up the Rheo Knee with Össur Logic and train you in the training area at our premises: walking on the level, stairs, a ramp, sitting down and standing up. With regular check-ups we keep refining the settings as the knee “learns” your gait and you get used to it.
What to expect in the first few weeks
At first, the Rheo Knee needs a little time to “learn” your gait, and you need time to trust its support. Many users notice that, as the days go by, they need to think less about every step. The exercise programme in the Össur Logic app helps you keep practising at home, and at follow-up visits we adjust the settings based on your experience.
Cost and EOPYY
The price of the Rheo Knee depends on the overall configuration of the prosthesis: socket, silicone liner, suspension system and prosthetic foot. EOPYY (ΕΟΠΥΥ), Greece’s national health insurance organisation, reimburses people insured in Greece for components according to the categories and maximum prices in its price list, with a co-payment by the insured person of, as a rule, 25%. There is no provision for full cover of a microprocessor knee: the difference is paid by the patient. We will tell you the exact amount in your case. Find out more on our pages on EOPYY reimbursement and our bionic knee comparison. If you are not insured in Greece, EOPYY reimbursement does not apply; you can pay privately, and any cover depends on your own insurer’s rules — contact us and we will give you the information you need for your case. The EOPYY information is correct as of the date this page was last updated (October 2026).
To find out together whether the Rheo Knee is right for you, book an assessment. See also all the systems in our bionic technology section and Össur’s active Power Knee.
How much does a Rheo Knee cost?
The price depends on the version of the knee and the other components of the prosthesis. We give a price after an assessment, with a detailed proposal that also shows the amount covered by EOPYY, up to its price-list category, for people insured in Greece. The patient pays the difference. Call us on +30 2310 282 894 to book an appointment.
What is magnetorheological fluid?
It is a fluid containing microscopic metal particles that becomes “thicker” or “thinner” within fractions of a second when the magnetic field changes. In the Rheo Knee this works like an electronic brake, controlling how easily the knee bends in each phase of the step.
Can the Rheo Knee get wet?
The Rheo Knee is weather-resistant and can be used in the rain and in wet conditions. However, it is not waterproof for immersion, so it must not go in the sea, the pool or the shower. If you want to take part in water activities, talk to us about a dedicated solution.
Does EOPYY cover the Rheo Knee?
EOPYY reimburses people insured in Greece for above-knee prosthesis components according to the categories and maximum prices in its price list, with a co-payment of, as a rule, 25%. There is no provision for full cover of a microprocessor knee. If you are not insured in Greece, EOPYY does not apply. Contact us and we will check what applies in your case. See our EOPYY page.
What is the difference between the Rheo Knee and the Power Knee?
The Rheo Knee is a passive microprocessor knee: it controls resistance, but you generate the movement. The Power Knee has a motor and adds active power, for example when rising from a chair and on stairs. Which one suits you depends on your strength, stamina and goals.
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We work with the leading manufacturers
Ask us about the Rheo Knee
Book an assessment on +30 2310 282 894 and find out whether the Rheo Knee is right for you and what EOPYY covers if you are insured in Greece.