What is a Partial Knee Replacement?

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  • Written By: Jacquelyn Gilchrist
  • Edited By: Michelle Arevalo
  • Last Modified Date: 11 February 2020
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A partial knee replacement is a surgical procedure that is also sometimes called a unicompartmental knee arthroplasty (UKA). As opposed to a total knee replacement, only part of the knee is replaced in this procedure. Typically it involves replacement of the outside part of the knee, also known as the lateral compartment, or the inside part, also called the medial compartment.

Severe arthritis that causes persistent pain is one reason for a partial knee replacement. This procedure may also be considered for patients with a knee deformity or a softening of the bones, also known as osteomalacia. A partial knee replacement is often preferable to a total knee replacement, because it requires a smaller incision, less bone is removed, and the recovery time is usually shorter.

Despite the benefits of this procedure, not every patient may be a good candidate for it. If the patient has advanced, widespread arthritis, this procedure may fail. Conservative treatments should be tried before surgery is considered, such as medications, physical therapy, and weight loss. In addition, ideal candidates are relatively sedentary, older than age 55, and have healthy ligaments.

To prepare for a partial knee replacement, the patient will be given anesthesia. A local anesthestic may be used, in which case the patient’s legs will be numb. Or the patient may be rendered unconscious with general anesthesia. The surgeon will then disinfect the skin on and around the knee.


After cleansing the area, the surgeon makes an incision about 3 in (7.62 cm) long. The damaged or diseased bone is removed. An implant, or prosthesis, is inserted into the area. This implant is generally composed of metal and plastic. After the implant is secured, the surgeon closes the incision with stitches.

Patients are often able to return home on the day of surgery or the following day, however, they should have someone else drive. Recovering patients are encouraged to maintain low levels of physical activity, such as walking around the house. A cane or walker may be needed for the first one to two weeks after the surgery. The doctor may recommend physical therapy. Each patient’s physical therapy program will vary, depending on his abilities, level of physical activity, and age.

Before having a partial knee replacement, patients should be aware of the possible risks involved. Patients may experience reactions to medications or to the anesthesia. They may have problems breathing. All surgeries carry the risk of infection and bleeding.

A partial knee replacement may also result in pain while kneeling, and an accumulation of fluid in the area. Patients may also experience damage to the blood vessels or nerves. In some cases, the implant may fail. Sometimes, after beginning the surgery, the surgeon may re-evaluate the damaged knee and rule out the possibility of a partial knee replacement. A total knee replacement may be needed instead in such cases.



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