Is Partial Knee Replacement Right For You?

Minimally invasive partial knee surgery

partial knee
A partial knee replacement does not resurface the entire joint. BSIP/UIG / Getty Images

Partial knee replacement, also called a unicompartmental knee replacement, is a surgery that may be considered for treatment of severe arthritis of the knee. Traditionally, patients with advanced arthritis of the joint would undergo total knee replacement. In a total knee replacement, all of the cartilage is removed from the knee joint, and a metal and plastic implant is inserted.

The partial knee replacement surgical procedure has generated significant interest because it uses a smaller incision and has faster recovery than full knee replacement surgery.

Partial knee replacement is a type of and minimally invasive surgery. The idea is to remove only the most damaged areas of cartilage from the joint, and leave any healthy parts of the joint for continued use.

Most often, partial knee replacements use implants placed between the end of the thigh bone and the top of the shin bone. Partial knee replacements can also replace the part of the joint under the kneecap, a patellofemoral replacement.

Is Partial Right For You?

The minimally invasive partial knee replacement is designed for patients who have severe arthritis of the knee that have not found relief with standard non-surgical treatments. The treatments may include oral medications, cortisone injections, strengthening exercises, and weight loss. If these treatments are not sufficient, and you are not satisfied, then surgery may be considered.

The partial knee surgery may be possible if the arthritis in the knee is confined to a limited area.

If the arthritis is more widespread, then the partial knee replacement is not appropriate, and should not be considered. In addition, the partial knee surgery is recommended in patients who are:

  • Older than 55 years
  • Not overweight
  • Not heavy laborers or athletes
  • Have intact ligaments (specifically the ACL)

    If these criteria are not met, then the minimally invasive partial knee surgery may not be as successful. Unfortunately, many patients are therefore ineligible for this procedure.

    The Downside of Partial Replacements

    Many patients who are interested in a partial knee replacement have arthritis that is too advanced for this procedure. Because surgical treatment is considered a last-resort by most patients, by the time surgery is necessary, their arthritis may be too advanced to consider the partial knee surgery. If partial knee replacement is done in a patient who is a poor candidate, failure rates can be high, and conversion to a total knee replacement may be necessary.

    Benefits of Partial Knee Replacement

    • Smaller Incision
      A traditional knee replacement surgery involves an incision about 8 inches over the front of the knee. There is more significant dissection necessary to complete the procedure compared to the partial knee surgery. In the minimally invasive partial knee replacement, the incision is about 4 inches, and the amount of dissection and bone removal is much smaller.
    • Less Blood Loss
      Because of the extent of dissection and bone removal necessary for a total knee replacement, the need for a blood transfusion is relatively common. With the partial knee procedure, a blood transfusion is infrequently needed, and patients do not need to consider giving blood before surgery.
    • Shorter Recovery
      Both the time in hospital and the time to functional recovery are less with the partial knee replacement. Patients are known to have been discharged on the day of the procedure, although most often patients are discharged on the first or second post-operative day. With traditional total knee replacement, patients seldom leave before three days in the hospital, and may require a stay in an in-patient rehabilitation unit.

    The long-term results are very good when partial knee replacement is done in the right patients. Older studies showed less successful results, but these results are thought to be due to poor patient selection. If the procedure is done on a patient with too widespread arthritis, the results are very likely to be less than satisfactory. If your doctor does not recommend a partial knee replacement, you may be in this situation. If this is the case, further conservative treatment (e.g. injections, physical therapy, medications, etc.), or total knee surgery are the best options.

    Conversion to Total Knee Replacement

    When patients with a partial knee replacement are properly selected, the minimally invasive procedure is quite successful. That said, some patients continue to develop arthritis in other areas of the knee. Also, some patients wear out the unicompartmental knee implant, or it can come loose within the knee. All of these situations would require additional surgery, and possibly the conversion to a total knee surgery. Conversion from a partial knee replacement to a full knee replacement can be more difficult because of the prior surgery, but it is not uncommon and results of conversion are good.

    Other potential problems with partial knee replacement a similar to risks of all joint replacements including infection, blood clots, and problems with anesthesia. It is important to have a discussion with your doctor about the risks of this surgical procedure.

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