Introduction to Knee Replacement

When a joint is irreparably worn, it is now possible to replace either part of, or the entire joint, with man-made components. It is important to understand the role of the anterior and posterior cruciate ligaments in driving normal knee function (kinematics). In total knee replacement, the anterior and posterior cruciate ligaments are removed and thus the knee no longer has normal knee function, although it can work exceedingly well and be a very satisfactory knee in a low activity person.

Partial knee replacements, however, have been designed to preserve the anterior and posterior cruciate ligaments. Knee function is thus more closely normal. With more normal kinematics, knee motion is superior to that of a total knee replacement. Partial knee replacement, however, can only be used if only a portion of the knee is worn out. If the entire knee is worn or crooked, then a partial knee replacement would be obviously inadequate.

Partial knee replacement: Partial knee replacement has actually been around longer than total knee replacement. The first partial knee replacements were performed in the 1950’s. Technically, partial knee replacement is more difficult than total knee replacement as one is preserving the cruciate ligaments, and the surgeon does not have control of the entire knee, only the worn out area.

There are 3 main areas where knees wear: The medial side (inside of the knee), the lateral Side (outside of the knee) and the knee cap (patellofemoral joint). Each of these 3 regions can be replaced individually or in combination.

Total knee replacement: This is the most common knee replacement surgery with approximately 3.2 million cases being performed in the United States annually. This operation replaces the entire distal femur (lower end of the thigh bone) and the entire proximal tibial plateau (upper end of the shin bone), realigning and resurfacing the knee. The anterior and posterior cruciate ligaments must be removed, but for a lower activity person the results are very satisfactory providing a virtually pain-free, totally functional knee.