What is a Prosthetic Knee?

A prosthetic knee is a mechanical device that replaces a knee that, for one reason or another, is no longer functional. Many people who suffer from severe knee pain or have serious knee damage have knee replacement surgeries. Such surgeries can restore a great deal of an individual's mobility, and are able to restore fairly active lifestyles to many people.

During a knee replacement, a surgeon removes the damaged bone and cartilage and replaces them with a man-made prosthesis. Having a prosthetic knee may prevent one from engaging in many physically-demanding activities such as jogging and various impact sports. There is no perfect prosthetic knee, and new versions are constantly being developed. Some utilize hydraulics, some are purely mechanical, and still others are computerized.

Knees are among the most complex of prostheses. Prosthetic limbs are, of course, complicated, but they do not serve the vast array of purposes that the knee serves. The knee must allow for smooth movement when a person walks, and must also give support when a person stands. It must have a range of motion that allows a person to sit, stand, or kneel. There is no single, ideal prosthetic knee because the purpose of the knee is far too complex to fully address with one design.

There are more than 100 different prosthetic knee designs to choose from. Doctors work with patients to choose the best fit, taking such things as age, weight, activity level, gender, and height into consideration. Some people choose a simple mechanical knee. This type of prosthesis has been in use for decades. Others choose a more advanced computerized knee that allows for precise corrections in the areas of stability and motion control.

Mechanical knees have no electrical or computerized components and come in many different forms. Some are single-axis, and work like a simple joint. These are the least expensive and require little maintenance, but they can not offer the stability of other prosthetic knee types. Some are polycentric, offering greater stability and a better degree of motion. Some mechanical knees lock manually, some are pneumatic, and some are even hydraulic.

More recently, engineers have designed computerized prosthetic knees. These computerized prostheses have microprocessors and integrated fluid systems. In essence, the computerized aspects of the knee “learn” the details of the individual's gait and adjust the fluid control system accordingly. Computerized prostheses tend to be lighter, more stable, and more expensive than their purely-mechanical counterparts. They are generally used by more active individuals.

While there is no perfect prosthetic knee, scientists and engineers have gone a long way toward making the best knee possible. With the advent of computerized prostheses, an easily-accessible and efficient man-made knee can not be too far off. Soon, perhaps, people with prostheses will be running once more.