Partial Knee Replacement

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Please copy/paste the following text to properly cite this HowStuffWorks article:

ADAM. "Partial Knee Replacement." 16 May 2007. HowStuffWorks.com. <http://healthguide.howstuffworks.com/knee-replacement-partial-dictionary.htm> 02 December 2009.

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Definition

Unicompartmental knee arthroplasty (UKA) is a minimally-invasive procedure to replace one of the knee’s three parts (thighbone, shinbone, or kneecap) to restore function. Because only part of the damaged knee is replaced, it is often called a partial knee replacement.

Alternative Names

Unicompartmental knee arthroplasty; Unicondylar knee replacement; Arthroplasty - unicompartmental knee

Description

At the hospital, the patient will be given either general (unconscious) or local (awake but no pain) anesthesia. A small cut (incision), typically about three inches, is made over the area of the knee that is damaged. The damaged bone is removed and replaced with an implant (prosthetic) made of plastic and metal. The thigh and shin bone may be slightly sculpted to fit the implant. Once the implant is in the proper place, it is secured with bone cement, and the wound is closed with stitches.

The operation takes about an hour to 90 minutes.

UKA has gone under significant revision since first performed in the 1970s. Today, the procedure offers many benefits over total knee replacement:

A smaller incision. The incision used in UKA is about 2 to 3 times smaller than the one required by total knee replacement. A smaller cut means less blood loss, less tissue damage, and a faster recovery.
Better range of motion after surgery.
Shorter hospital stay.
Costs less. UKA costs about half that of total knee replacement.
If needed, the implant can be easily converted to a total knee replacement.

Pain relief is the same for both procedures.

Indications

Certain diseases and conditions can affect knee function. The most common reason for UKA is arthritis.

Unicompartmental knee arthroplasty may be considered in patients with the following conditions:

Osteoarthritis of the knee
Knee deformity
Refractory osteomalacia
Avascular and aseptic necrosis

Patients age 60 and up who are not physically active and who have no history of inflammatory arthritis are good candidates for this procedure. UKA is not recommended for patients who engage in heavy work or sports, are obese, or have significant ligament problems.

Risks

Risks for anesthesia include:

Reactions to medications
Problems breathing

Risks for any surgery include:

Bleeding
Infection

Risks specific to UKA include:

Deep vein thrombosis
Nerve and blood vessel damage
Implant failure
Reflex sympathetic dystrophy (rare)
Fluid build-up in the knee joint
Pain with kneeling

Expectations after surgery

Most patients have a rapid recovery and have considerably less pain than they did before surgery.

Convalescence

Most patients go home the day after surgery (unlike the 3 or 4 days required by a total knee replacement). You can put your full weight on your knee immediately. There is usually less rehabilitation or physical therapy required compared to total knee replacement. Most forms of exercise are acceptable after surgery, including walking, swimming and biking. However, patients should avoid high-impact activities such as jogging.

References

Berger RA, Meneghini RM, Jacobs JJ, et al. Results of unicompartmental knee arthroplasty at a minimum of ten years of follow-up. J Bone Joint Surg Am. 2005 May;87(5):999-1006.

Patil S, Colwell CW Jr, Ezzet KA, et al. Can normal knee kinematics be restored with unicompartmental knee replacement? J Bone Joint Surg Am. 2005 Feb;87(2):332-8.

Review Date:7/1/2005
Reviewed By: Kevin B. Freedman, MD, MSCE, Sports Medicine, Orthopaedic Specialists, Bryn Mawr, PA. Review provided by VeriMed Healthcare Network.