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Partial Knee Replacement

Alternative names: Unicompartmental Knee Replacement, Minimally Invasive Knee Surgery

What is a partial knee replacement?

Partial knee replacement is a procedure in which orthopaedic surgeons replace part of a painful, dysfunctional knee joint that has only either the inner (medial) or outer (lateral) part of the joint damaged. A limited surgical procedure can resurface only the affected area with a metal implant and can preserve the remainder of the otherwise healthy knee.

Why would a doctor recommend a partial knee replacement?

Partial knee replacement is usually recommended in patients who have severe arthritis of the knee and who have not benefited from conservative treatments such as medication, injections, strengthening exercises, and weight loss. In addition, it is only normally recommended in patients who:

  • Have arthritis that is confined to a limited area of the knee
  • Have intact ligaments (specifically the ACL)

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

What does partial knee replacement surgery involve?

Before surgery you will have some pre-operation appointments, which your provider will give you information about. On the day of your surgery, after admission, you will be evaluated by a member of the anesthesia team. The most common types of anesthesia are general anesthesia, in which you are asleep throughout the procedure, and spinal or epidural anesthesia, in which you are awake but your legs are anesthetized. With your input, the anesthesia team will determine which type of anesthesia is best for you.

The surgery takes about one and a half hours. An incision is made over the knee and the worn-out cartilage is exposed. The rough edges of the end of the femur (a bone that goes from the hip to the knee) and top of the tibia (a bone that goes from the knee to the ankle) are cut flat, cleaned, and then the unicompartmental device is cemented in place.

How long is the recovery after partial knee replacement surgery?

After your surgery, you can expect to start rehab almost immediately. Patients usually stay in the hospital for one or two nights but putting weight on your knee is usually permitted immediately. Exercise training will depend on the age and activity level of the patient and are customized to that patient's abilities. At a follow-up appointments with your surgeon, you will get a better idea of the actual length of time to your full recovery, and it depends largely on your regaining your muscle strength.

Several studies have demonstrated the advantages of this treatment option over the more conventional total knee replacement. These include: a smaller scar, less pain, a potentially shorter hospital stay, a faster rehab and recovery time, and possibly a greater range of motion when compared to standard total knee procedures. In addition, because more of the knee remains untouched, patients often report that the knee feels more normal to them.

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