Tuesday, April 1, 2014

from the Doctor's Desk: What is a partial knee replacement?

What is a partial knee replacement?
How is it different from a total knee replacement?

 A partial knee replacement means that rather than replacing all of the knee’s joint surfaces, we replace only the area that is affected by arthritis.  It’s useful to understand that a joint replacement is really a resurfacing of the joint in the area that is worn down (the cartilage is thin and there is a loss of padding and smooth surface between the bones).  The worn cartilage and a relatively thin layer of bone are replaced with metal and a hard plastic spacer.
Image from AAOS website

The most common partial knee replacement is a unicondylar (unicompartmental) replacement where the inner (medial) portion of the knee is replaced.  In the procedure the outer (lateral) portion of the knee and the kneecap joint area are not replaced.  In addition, the internal ligaments are also left in place.  Less commonly performed is a patellofemoral replacement (kneecap joint).  In this procedure the inner and outer portions of the knee and the internal ligaments are left alone and only the kneecap area replaced.

The best candidates for partial knee replacement are those with arthritis and pain that’s relatively localized to one region of the knee.  If arthritic changes are much more widespread, then a total knee replacement is a better option.  With a partial knee replacement there is a chance for progression of knee arthritis in the rest of the knee that could require a conversion to a total knee replacement.  However, with good patient selection, many partial knee replacements are working well for patients for 15 years or more.

Image from AAOS website
The benefits of a partial knee replacement typically include a faster and less painful recovery and a knee that may feel “more normal” than one with a total knee replacement.  For example, many partial knee replacements only need one night in the hospital versus two with a total knee replacement.  There is a growing trend to perform partial knee replacements given their overall good outcomes in the right patients.

Dane Glueck, MD – April 2014

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