Partial Knee Replacement Surgery

If you are considering knee surgery, the following partial knee replacement information may help you understand your alternatives.

Knee pain from arthritis can be particularly debilitating because we use our knees in almost all of our daily activities. If you are experiencing severe knee pain that interferes with your normal functioning, your doctor may recommend a partial knee replacement, also known as unicompartmental knee replacement.

This procedure is much less invasive than total knee replacement and may give relief to people suffering from arthritis of the knee or a knee injury. Partial knee replacement surgery replaces only the damaged area of your knee joint, may require only one or two days of hospitalization, and results in a shorter recovery time when compared with total knee replacement surgery.

The knee can be divided into three compartments: the medial compartment - the inside part of your knee, the lateral compartment - the outside part of your knee, and the patello-femoral compartment - the area where your kneecap rests. The unicompartmental implant is designed to replace either the media (inside) or lateral (outside) compartment.

The X-ray below left shows a right leg with a degenerated medial (inside) compartment. Notice how there is no space between the femur (thigh) bone and tibia (shin) bone. This bone on bone contact can be quite painful.

The X-ray above right was taken after a partial knee replacement. A metal and plastic implant provides a cushion where the bone on bone contact was. The surgery restores normal alignment to the leg and relieves abnormal stresses to the body.

Available Treatment Options

Your doctor may try several conservative treatments before recommending partial knee replacement.

If the conservative treatments do not relieve your pain from knee arthritis, surgical procedures may be recommended. Knee arthroscopy is a minimally invasive procedure to remove debris or repair torn cartilage. Total knee replacement surgery is major surgery that replaces all three compartments of the knee. Between those two alternatives is partial knee replacement surgery.

Minimally Invasive Partial Knee Replacement

The unicompartmental knee replacement is a minimally invasive option for patients with knee arthritis that is isolated to either the inside or outside compartment of the knee. This minimally invasive procedure provides several benefits to patients who have a moderately active lifestyle, are within normal weight ranges, and have arthritis that is confined to a single compartment.

There are many benefits to unicompartmental knee replacement.
First, the procedure leaves a 3-4 inch incision, compared to an 8-12 inch incision for conventional (non MIS) total knee replacement.

There is no dislocation of the patella (kneecap) during the procedure, which leads to less pain and a more rapid rehabilitation.

There is minimal blood loss in a partial knee replacement. The procedure causes less post-operative pain and a lot shorter hospital stay compared to a total knee replacement.

There is also a reduced need for analgesia and post-operative medication.

After the surgery, patients may be able to walk within 3 to 4 hours and experience a much faster rehabilitation and recovery - 2 to 5 weeks for many patients. After achieving full recovery, most patients experience an increased range of motion when compared to total knee replacement.

The Procedure

The partial knee replacement procedure begins with the exposure of the joint through a 3-4 inch incision. The surgeon then properly balances the knee joint. Next the surgeon shapes the end of the thigh bone (femur) and the top of the shin bone (tibia) to accommodate the unicompartmental knee replacement components. He places trial components on the bones to ensure proper alignment and removes them once this alignment is achieved. Finally, the surgeon implants the femoral and tibial components, closes the incision, and the procedure is complete.

Returning Home

You will be discharged when you can get out of bed on your own and walk with a walker or crutches, walk up and down three steps, bend your knee 90 degrees, and straighten your knee.

You will continue your home exercise program and go to outpatient physical therapy, where you will work on an advanced strengthening program and such programs as stationary cycling, walking, and aquatic therapy.

Your long-term rehabilitation goals are a range of motion from 100-120 degrees of knee flexion, mild or no pain with walking or other functional activities, and independence in all activities of daily living.