Different Types of Prosthetic Knees Available

There are many types and brands of knees and shins available on the market. The selections pictured below are just used to give the new amputee an introduction to what is available on the market.

For above the knee (AK) amputee, there are three basic types of knee and frame/shin technologies available:

1. Polycentric (simple mechanical, friction)
2. Hydraulic (fluid, mechanical)
3. Electronic (microprocessor, fluid, mechanical)

See also knee rotators, vertical shock pylons, rotating torsion adapters and pin-locks.

1. Polycentric knees: (the least expensive)
This type of low maintenance knee is often used by new amputees, but walking during the "swing-phase" (extending your leg) is not nearly as natural as when using a hydraulic type of knee as shown in the hydraulic section further below. Other than spring-loaded friction, polycentic knees offer little or no "stance control". Stance control is a highly desirable feature that prevents a knee from accidentally buckling-under when you least expect it. Some polycentric knees provide a simple locking mechanism so that the knee can be temporarily locked in the extended (straight) position.

The simplest form of polycentric knee joint

Cascade Orthopedic Supply polycentric.........

Model 1920 Polymer friction control, and Children's 4-bar knee from TotalKnee.com

GeoFlex™ Knee from Ohio Willow Wood

2. Hydraulic knee shins and cylinders:
In my opinion, hydraulic knees are the best type available from the overall perspective. They are relatively low maintenance, and offer a very natural gait (walking) characteristic. Both the extension (straightening) and flexion (bending) are independently hydraulically adjustable. These also feature "stance control" to prevent the leg from buckling out from under you. When selecting a knee, get one with the largest flexion (bending) range of motion available (normally 135 degrees). These hydraulic knee cylinders can be locked in any position. The hydraulic unit can also be temporarily disabled so that the legs swings freely. This feature is often used when riding a bicycle or other activity when the hydraulic action would actually hinder the activity.

A Ca-Tech "CaStance" Hydraulic Cylinder mounted on an Endolite 160HA (high-activity) knee

Mauch, The Hydraulik SNS® Mauch "GaitMaster" Frame has "stance control"

The Otto Bock single-axis 3R80 modular rotary hydraulic knee joint has a newly developed rotational hydraulic system and a relocated rotation point. Besides the hydraulic swing-phase control, this knee joint permits adjustable, fluid-controlled knee flexion with weight-activated stance-phase stability. Generous 135 degree flexion angle. Independently adjustable hydraulic flexion and extension resistance.

Symbiotechsusa.com "XT9" Extreme Activity Energy-storing featuring "Quad Mimic" and "Extension Assist/Promote" Control

Permits amputees to Telemark ski, skate, surf, snowboard, rock-climb and participate in many other high-activity sports. The adjustable coil-over, air-shock absorbs impact when landing and automatically provides lower leg "extension" that normally the quadriceps muscle would perform. Symbiotechsusa.com

Ohio Willow Wood "Pendulum" hydraulic varieties.......

Hybrid 4-bar hydraulic knee from TotalKnee.com

The "510 Nylon Knee" from Aulie Devices uses a combination of cylinder type clamping mechanism to control the extension and flexion of the leg, as well as friction control. A very nice feature of this knee is that it is 100% waterproof so you can get it wet and even swim with it. Flexion angle is 160 degrees.

Mr. Alan Aulie
Aulie Devices, Inc.
3615 Northwest Way
P.O. Box 786
Redmond, Oregon 97756
Phone/Fax: (541) 548-7355 E-mail: aaulie@coinet.com

3. Electronic knees: (Very functional, but the most expensive type, and most high maintenance)

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