Prosthetic knee systems are among the most complex of all components. This is because knees must give support when people stand, allow smooth motion when people walk, and permit movement when people sit, bend or kneel.
Prosthetic knees range from simple systems that have been used for hundreds of years to advanced computer-based systems that are popular today. While the perfect prosthetic knee has yet to be invented, research shows great promise with many new types of technology.
Today, there are over 100 types of knee systems to choose from. Doctors, prosthetists and rehabilitation specialists consider an amputee’s age, health, activity level, and lifestyle when making suggestions about which types of knees and their options for stability and motion control would work best for them.
There are two major types of knees — mechanical and computerized. Each type has advantages (what works well) and disadvantages (what doesn’t work as well).
Mechanical knees can also be divided into two types: single-axis and polycentric (more than one axis).
Single-axis knee. This type of knee works like a simple hinge. It:
Polycentric knee. This type of knee is more complex, allowing more freedom of motion. It also:
There are two types of stability options for mechanical knees — manual locking knees and weight-activated stance-control knees.
Manual locking knee. This type of knee:
Weight-activated stance-control knee. This type of knee:
Motion Control Options
All knee systems need some type of swing control to keep a steady gait. There are two options — constant friction and variable friction motion control.
Constant friction. These systems:
Variable friction. These systems:
Fluid Control Systems
Fluid control systems work like pistons to provide varying degrees of resistance during swing phase, allowing amputees to walk comfortably at different speeds. There are two types of fluid control systems — pneumatic (using air) and hydraulic (using fluid).
Pneumatic control. These systems:
Hydraulic control. These systems:
COMPUTERIZED (MICROPROCESSOR) KNEES
Computerized knees are relatively new types of prosthetic technology. There are several types now available, and others are in development. Although each model has slightly different features and performance characteristics, all computerized knees:
Translated from Prosthetic Knee Systems
Disclaimer: The views and opinions expressed in this publication are those of the authors and are not necessarily those of the Amputee Coalition, the Department of the Army, the Army Medical Department, or any other agency of the US Government.
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