Petrus Mnisi’s New Found Freedom and Peace of Mind

Petrus Mnisi is a transfemoral amputee and has been for many years. Over the time that has elapsed since his amputation, he has developed his own gait pattern. This is a common way that amputees cultivate a gait that allows them to feel safe and secure while walking.

The many years as an amputee have resulted in a habitual gait pattern forming, likely due to the fact that Petrus has always had mechanical knee joints. At Deist & Associates, we recently fit Petrus Mnisi with his very own RHEO XC knee joint.











The Difference Between Mechanical and Microprocessor Knees

Mechanical Knees

This style of prosthetic is governed by a mechanical hinge (hence the name) which is controlled by one of the following mechanisms within the system:

  • Free swing
  • Manual lock
  • Constant friction
  • Weight-activated friction
  • Geometric locking
  • Hydraulics

Microprocessor Knees

Where the mechanical knee uses one of the above-listed mechanisms, the microprocessor knee makes use of a sensor to control the gait and the way the knee swings. It has the ability to provide resistance when walking downhill, sitting down or walking downstairs. It allows the wearer to use less energy while walking and standing as well as a much-needed sense of security when moving.

Petrus’ First Steps with the RHEO XC Knee Joint


Petrus Walking Downhill



The video is not to boast the way in which Petrus walks, but instead to showcase his surprise and excitement when he feels the sensation of security provided by the RHEO XC knee joint. It provides a resistance when climbing stairs and walking downhill that he did not have with his previous prosthetics. His reaction to this new peace of mind provided by his feeling of safety is nothing short of priceless.


Petrus Walking Downstairs



When walking downhill or sitting down with his previous prosthetic leg Petrus had to lead with his sound leg (which is a difficult habit to break).

These videos document the first time Petrus uses his new prosthetic to walk down a hill, sit down and walk downstairs. Petrus’ RHEO XC is still in the test-socket phase. Jaco Deist says:

Petrus Sitting Down





Petrus’ reaction is so inspiring and an honour to experience.


We will keep you updated on Petrus’ progress in the months to come. For more information read our blog or contact us to see how Deist & Associates Prosthetic Centre can help you and your loved ones.