Partial Knee Replacement


Who is a candidate for partial knee replacement?

Patients with advanced arthritis in one compartment of the knee of any age can be candidates for partial knee replacement surgery. It is important that the pain and arthritic changes are confined to one compartment of the knee. In addition, we only consider patients with relatively good range of motion and patients that do not have excessive deformity of the knee candidates for partial knee replacement since the options of restoring alignment and range of motion for patients with very stiff or deformed knees are limited with a partial knee replacement. In addition, a partial knee replacement might not be indicated in very heavy patients beyond 200 to 250 pounds or patients with inflammatory arthropathies.

What is a partial knee replacement?

A partial knee replacement is the implantation of an artificial joint in only one compartment of the knee. A partial knee replacement can be performed for either the medial or lateral compartment or the patellofemoral compartment. Most partial knee replacements are fixed using cement and metal on plastic is the most common bearing option.

What is the benefit of partial knee replacement?

The main benefit of partial knee replacement is that it is a less traumatic surgery that has considerable less risks than a total knee replacement and allows the patient to return to his activities faster than standard total knee replacement surgery. Most patients after will regain their range of motion and ability to walk within two weeks after the surgery and will often be able to return to work within the first two to four weeks after surgery. The medical risks including the risk for blood clots and the risk of blood transfusion is significantly lower than for patients undergoing total knee replacement.

What is the main risk of partial knee replacement surgery?

The main risk of partial knee replacement is that over time arthritis can affect the other compartments of the knee and patients might develop pain secondary to progression of arthritis in the other compartments which might ultimately require revision of the partial knee replacement to a total knee replacement. Modern partial knee replacements often have longevity beyond 10 or 15 years and the risk of revision surgery is rather low within the first 15 years. Therefore, partial knee replacement might be an especially appealing option for older patients or very young patients that one way or the other will face the risk of revision surgery. Other complications of partial knee replacement are related to the surgery itself and can include neurovascular injury to the neurovascular structures, intraoperative fractures, malalignment of the components or loosening of the component requiring revision surgery. In addition, patients with a partial knee replacement can develop postoperative infections which might require removal of the components and antibiotic treatment. Overall, the risk of medical or surgical complications is lower with partial knee replacement than with total knee replacement.

What does it entail to have a partial knee replacement surgery?

Well usually after you undergo medical clearance you are admitted to the hospital the day of your surgery. You will then undergo a spinal anesthesia, a regional anesthesia that allows to be mobilized the day of surgery and has less risks than general anesthesia. The surgery itself takes about 30 to 45 minutes and after the surgery you initially will be transferred to a postoperative recovery room where your vital signs and the weaning of the anesthesia is monitored by an anesthesiologist. You are then transferred to the floor where we immediately start physical therapy and rehabilitation. Usually within one day you are able to leave the hospital. Dr. Boettner in general recommends that you go home after surgery where he will provide you with a CPM machine and a therapist that will check on you during the week to make sure that you achieve adequate physical therapy. By the time you leave the hospital, your knees should achieve at least 90 degrees of range of motion, you should be able to walk 100 feet with either a cane or walker and you should be able to walk a flight of stairs. By the time of discharge, your incision should be dry.

Do I need to go to an in-house rehabilitation facility after partial knee replacement?

Most patients will return home within one or two days after partial knee replacement surgery. Only patients that require assistance at home should consider going to inpatient rehab. The majority of patients will be able to return home after surgery.

How is a partial knee replacement performed?

Today partial knee replacements can be performed using robotic-assisted surgery. This allows the surgeon to plan the surgery based on preoperative CT scans and intraoperative physical exam and then allows the implantation of the component in a very precise manner utilizing a robotic arm with a burr. This allows for optimized component alignment and fixation. Dr. Boettner is also using manually implanted partial knee replacements. Please discuss which implant is right for you with him.

What are other advantages of partial knee replacement?

Besides faster rehabilitation, the main advantages of partial knee replacement is that the patients will be able to regain better range of motion than after total knee replacement surgery. Most patients will reach more than 130 degrees of flexion and will come close to their natural range of motion. In addition, partial knee replacement is less traumatic, is associated with less blood loss and therefore has less impact on the overall health and facilitates faster return to normal activities. Partial knee replacement preserves the anterior and posterior cruciate ligament which are usually resected when a total knee replacement is performed and therefore preserves the normal kinematic and motion of the knee which likely results in better overall function of partial knee replacements.

Do I need to be on a blood thinner after a partial knee replacement?

We usually just use 325 mg of aspirin twice a day for the first three to four weeks after surgery for blood clot prophylaxis. While most patients undergoing total knee replacements require Coumadin and repeat blood draws after surgery, this is rarely indicated in patients with a partial knee replacement.