Sports Injuries

Updated 15 May 2015

Amputee leads active life with bionic knee

Maretha Coetzee, a farmer from Namibia struggled for many years after losing her leg in a car accident. Her life changed for the better after she received a bionic knee, allowing her to live a more active, full life.

Trans-femoral amputee Maretha Coetzee – a farmer from the remote area of Stampriet in Namibia – lost her leg 17 years ago in a car accident while she was pregnant with her first son.

Coetzee’s right leg was amputated above the knee as a result of the injuries and since the accident she’s been struggling to find a suitable solution to regain her mobility and to restore her quality of life.

Bionic knee from Iceland

In the short, inspirational video below we see how a bionic knee from the Icelandic prosthetics and orthopaedics manufacturer – Össur – changed her life and enabled her to continue her physical day-to-day work as a farmer in a very remote and challenging environment.

Ossur Rheo Knee Vid 3

Maretha Coetzee tending to the animals on the farm with her bionic Rheo Knee 3

“When I first met Maretha, she was a very low activity patient,” says Mike Barkley, Coetzee’s prosthetist from George in the Southern Cape.

Read: Knee injuries

“She came to us because she was constantly having problems with the small hydraulic knee she was using at that stage. She was blowing valves and other components continuously and she was looking for an alternative.”

Barkley decided to fit Coetzee with the innovative, bionic Rheo Knee 3 from Össur, a computer-controlled prosthetic-system with a micro-processing knee-joint that aims to provide natural knee function by adapting to the user’s movements and environment.

Ossur Rheo Knee Vid 2

The Rheo Knee 3 is a computer-controlled prosthetic-system with a micro-processing knee joint allowing for more active use

How it works

The micro-processing knee-joint uses electromagnetically charged, magnetorheologic technology ("Ferro-fluid") as an actuator. The actuator is the mechanism by which the knee acts upon in a specific environment when controlling the swing movements and the static stance.

The knee joint is packed with integrated sensors that continuously measure both its angle and the load it is bearing at a rate of a 1000 times per second. The computer chip uses this data from the sensors to control the viscosity of the magnetic "Ferro-fluid".

Read: Jumper's knee

Tiny metal particles within the fluid form small chains when the magnetic field is turned on, causing the fluid to become thicker. That, in turn, affects the stiffness of the joint, which is modified constantly while the knee is moving, allowing for a smooth swing of the leg.

Given the specific data, the knee basically learns and adapts to the specific walking patterns and movements of the amputee.

Rheo 3 Knee

“Her feedback when she got the Rheo 3 Knee was that she could do so much more. She was using less energy in her daily activities on the farm,” says Barkley.

Watch this clip of Maretha's journey:

“Initially I was reluctant for her to use that knee because of the dusty conditions on the farm, but she’s disproved my reluctance… that knee’s really performing very well. One of the other concerns I had was that she runs two farms. The one farm didn’t have electricity and with the Rheo 3 having a three-day battery-life was a definite plus in her favour. She could go to that farm for three days without worrying about battery failure.”

Read More:

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Knee pain may run in the family

Knee replacement may go poorly for people who think life isn't fair

All images and words: William Welfare


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Sports Injuries Expert

Adrian Rotunno is a medical doctor in the Sports & Exercise Medicine fellowship at the Sports Science Institute of South Africa, and qualified physiotherapist. Team physician for Dimension Data pro-cycling, and Boland Rugby. Special interests include endurance sport, in particular cycling, as well as contact sports.

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