Ossur bionic prosthetics

I think it’s only natural to expect that one of the largest prosthetics manufacturers – Ossur would push the development further in their field. This is exactly what Ossur does to fulfill their company slogan – Life without limitations. Some of these developments are so technologically advanced that I’d feel really bad if I didn’t write about them on this site.

As you can understand, the most advanced solutions aren’t always the best option when price and performance are evaluated. Still, immediate application isn’t the main reason of research and development – to improve the future of humankind is the main reason.

And now, it really seems that the future we have dreamed of is quite near. Bionic products from Ossur are among first of their kind – they promise a better world, a world where people are able to restore natural abilities such as walking by putting technologies to a good use.

Bionic product line from Ossur goes under a brand name “Bionic Technology by Ossur”. Today there are three products in this line – the PROPRIO FOOT®, the RHEO KNEE® and the POWER KNEETM. As these names suggest – the first one is designed to replace a lost foot, while the other two devices are designed for above knee amputees.


Proprioception is used to describe a sense of the relative position of one’s body parts. Yesterday, I had to gather my thoughts a bit, so I lay on my sofa with one hand behind my head, after a while I wanted to touch that hand with my other hand, somehow I couldn’t find it for a moment! Don’t know why, but my proprioception was impaired at the moment.

Contrary to me on that occasion, some early testers of the new bionic foot by Ossur claimed to have a feeling of the foot in their heads – they knew where the foot is and how it would react to different situations. Thus it was called the PROPRIO FOOT to refer to proprioception experienced by users when using it.

The foot uses sensors such as accelometers the information gathered by its sensory system is then processed to determine how the PROPRIO FOOT’s actuators should respond in a given situation. The calculations are done continuously.

Therefore, the foot is able to facilitate more natural walking as well as react to different walking speeds and different terrains. Also, the foot can recognize and act accordingly when a user ascends or descends slopes or stairs. Only, the device can get confused if a slope is steeper than 20 degrees and express unwanted behavior in such cases.

It is not intended for sports or very active applications such as climbing, also it shouldn’t be submerged in water. It is designed for everyday use and its battery can handle it – a fully loaded battery supports 24-48 hours long usage. Other than that, it seems that it’s the most naturally acting foot prosthesis on the market.


Magnetorheological fluid is a fluid that reacts to magnetic field by changing its viscosity. The actuator used in the RHEO KNEE uses such fluid together with rotary blades to adjust the knee’s resistance as needed, hence its name – the RHEO KNEE.

The brand name under which these products are released – Bionic Technology by Ossur implies that numerous fields of science and engineering are fused together in order to develop these devices. The RHEO KNEE is not an exception.

So, it has a sensory system that monitors force, position and load applied to the knee. Then this information is evaluated and the most appropriate response is calculated by the software. The software is another strong side of this device, as extensive configuration is not needed. The knee is “smart” enough and continuously learns and adapts to a particular user.

The battery life is 24-48 hours for a fully charged knee. When there’s no power the knee will be in a free swing mode, it will not be in a stationary mode. Its settings can be adjusted using a PDA to whom it can connect using either a cable or a blue-tooth connection.


Software controlled prostheses such as the RHEO KNEE and the C-leg by Otto Bock are a significant leap compared to other prostheses whose swing-phase can be adjusted only manually. Still, there’s something more that could be achieved here.

When human’s legs are sound, muscles work to bend and straighten the knee. Muscle activity aids walking, ascending stairs and slopes and so on. The above mentioned prosthesis and the c-leg – both control the knee’s behavior but they don’t provide additional lifting force.

The POWER KNEE is designed to address this issue and develop artificial legs even further – it is the world’s first powered prosthesis for above knee amputees. It means that it can assist when a user is walking; it can facilitate getting up from a seating position, as well as provide active lifting power when ascending stairs.

The sensor system is interesting as well. In addition to sensors that reside in the knee, information is gathered from the sound leg as well. This is done using a special insole that is inserted in the shoe of the sound leg where it gathers information. This information is then being sent to the prosthesis.

Thus, the POWER KNEE by Ossur not only adjusts to conditions it senses directly, it mimics the sound leg as well. It also reduces fatigue when walking, as well as wear and tear of sound body parts that usually carry additional stresses.

As far as I know, it is quite expensive at the moment (if available at all). However, the chances are that the price point will go down sooner or later making such devices more accessible to a wider range of people.

the Future

As you understand, there still are many things that could and should be done to achieve the goal of restoring full capabilities to people who have lost them. People at Ossur have outlined where they intend to head in this field. Let me discuss these directions.

According to Ossur, they plan to develop the idea of motorized prosthetics that aid people in movement even further. In collaboration with their partners, Ossur researches other types of actuators such as artificial muscles.

Another direction is osseointegration. Osseointegration, basically, means implementation of a load bearing implant into a living bone, thus extending it and allowing to directly connect a prosthesis. This technique would eliminate many socket related problems, as well as improve the level of control the user has over his prosthesis.

Last but not least – there is a neurosensing direction. This direction deals with connecting prosthesis to a human’s neurological system. If this can be achieved (and there is a considerable amount of evidence that points out it can be done) a user could control his prosthesis the same way he would control a sound limb – by will.

So, what do we have when all this is put together? A fully functional artificial limb that can be used in the same way as those nature intended for us. I really hope that we will see this happen.

back to the present or the conclusion

While this hypothetical prosthesis that we can see when looking at directions where all this is heading is still in development and we cannot know for sure when something like that could be available, bionic prostheses like the PROPRIO FOOT and the RHEO KNEE by ossur as well as the C-leg by Otto Bock are available. These prostheses represent a great leap if we look back at what was available some 40 years ago. Let’s hope that the development pace gets even faster.

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