What is a partial knee replacement?

Partial knee replacements, as opposed to total knee replacements, only resurface or address the compartment within your knee, which is suffering from osteoarthritis.  Approximately 25% of patients with painful osteoarthritis of the knee are candidates for partial knee replacements.

 

Partial knee replacements are evolving more so than their total knee counterparts.  We now have the ability to replace one compartment, or even two compartments.  There are three compartments which compose the knee.  There is a medial or inner compartment.  There is a lateral, or outer compartment.  And there is the anterior compartment which is the surface under your patella.  Partial knee replacements can be performed on either the medial or lateral side or even the anterior or patella compartment.  There are currently two companies which make partial knee replacements, which will replace both the medial and the anterior compartment at the same time.

 

There are numerous advantages and disadvantages of a partial knee replacement.  If we are able to preserve all your native ligaments, your knee will feel much more natural and your ability to negotiate stairs and perform other activities will likely be better than in the patients who have undergone a total knee replacement.  As others have mentioned, one of the potential downsides is that the arthritis progresses and eventually your partial knee replacement may need to be converted to a total knee replacement.  Most surgeons, when considering a partial knee replacement, will let their patient know before going into the operating room that if arthritis is found in the other compartments that a total knee replacement will be performed, as opposed to a partial knee replacement, so that a conversion to a total knee replacement you will not need to take place within a few short years.

If your knee damage is limited to one of the bumps (condyles) on the end of your femur, you may benefit from a partial (unicompartmental) replacement that leaves the rest of the joint intact. This technology has been around for decades, but became more popular once surgeons were able to install the partial implant through a small incision (about three inches rather than eight) with minimal impact on muscles and ligaments—a surgery nicknamed the "mini-knee."

The potential advantages are clear: less blood loss, shorter hospitalization, and quicker recovery. However, a unicompartmental replacement lasts only about 10 years, compared with 15 to 20 years for a total knee replacement. They aren't well suited for people who are very bowlegged or knock-kneed. You may be offered this option only if damage is limited to one portion of the knee, if the damage results from a traumatic injury rather than arthritis, if your ligaments are intact, and if your knee still contains a fair amount of healthy cartilage. The ideal patient for this surgery remains an older, thinner person rather than a younger, more active one. It may be suggested to buy time before total knee replacement in someone young and active, however.