Partial Knee Replacement (Unicompartmental and Patellofemoral Replacement)
Your knee joint has three compartments, namely the inner (medial) compartment, the outer (lateral) compartment, and the anterior (patellofemoral) compartment under the kneecap. Arthritis (wearing out of the cartilage) of the knee can affect any one of these areas, alone or in combination.
The difference between a partial knee replacement as compared to a total knee replacement is that the surrounding normal cartilage and ligaments which are not worn out, are left alone and are not removed like they are in a total knee replacement. Like total knee replacement surgery, partial knee replacement provides considerable pain relief with advantages that include a shorter hospital stay (going home the same day) and a lower risk complications. In general, partial knee replacements have long-term success in terms of how long they last and how they function that is comparable to total knee replacement. However, most studies have demonstrated that partial knee replacements do have a higher rate of needing further surgery as compared to total knee replacements.
Typically, most patients who have worn cartilage in only one part of the knee will have pain limited to that specific area. There is typically minimal deformity and good knee range of motion. Standard x-rays and possibly an MRI are used to confirm the diagnosis.
If your symptoms, physical examination, and studies suggest that the arthritis is in only one part of the knee, you may be a candidate for a partial knee replacement. While most patients with knee arthritis are best treated with total knee replacement, there are some are excellent candidates for a partial knee replacement. A conversation with your surgeon will help you decide what is best for you.
This is a surgical procedure that requires a 3 to 4 inch surgical incision in the front of the knee. Only the surfaces of the worn cartilage is removed and replaced with a metal and plastic component. The metal implants are “cemented” in place. This is a surgery through a small incision and not arthroscopic surgery.
Most patients go home the same day, but on occasion, some will stay one night.
Follow up after surgery
If staples are used, they are removed 2 weeks after surgery with postoperative follow up typically at 4-6 weeks and 3 months, depending on surgeon preference.
How long will I remain on anticoagulation (blood thinners that help avoid blood clots)?
Typically 4 to 6 weeks after surgery. For most patients, aspirin is prescribed. For other patients, especially those who are unable to take aspirin, low-molecular weight heparin (Lovenox) or warfarin (Coumadin) are used. If you are on warfarin, you will need blood work drawn 1 to 2 times a week and your medical consultant will adjust your medication dosage. If you are placed on aspirin or low-molecular weight heparin injections, you will not require blood testing.
Is swelling of my knee, leg, foot, and ankle normal?
Yes, for three to six months. To decrease swelling, elevate your leg and apply ice for 20 minutes at a time (3-4 times a day).
Is it normal to feel numbness around the knee?
Yes, it is normal to feel numbness around the incision and outer side of the knee.
What exercise should I perform at home?
Please do exercises as instructed by your surgeon. Remember that if you are using your knee to do things, you are actually doing physical therapy for your knee.
How long will I need to use a cane?
This varies with each patient. Usually a cane is used between 2-6 weeks.
May I go outdoors prior to my first postoperative visit?
Yes, we encourage you to do so.
May I drive or ride in a car before my first postoperative visit?
Yes, you may ride in a car. However, you must be off all pain medications prior to driving. If your right knee is replaced, you should wait for 2 to 4 weeks before driving.
May I ride in an airplane before my first postoperative visit?
Yes, you may ride in an airplane. Be sure to pump your ankles up and down, get up and move around at frequent intervals. You may find it more comfortable in an aisle seat.
Why is my leg bruised?
It is common to have bruising on the skin. It is from the normal accumulation of blood after your surgery.
What is the maximum range an artificial knee can achieve?
This depends on your preoperative range-of-motion. Your final range-of-motion will be close to the range-of-motion that you had before the surgery.
Complications can occur with all knee replacement surgeries, but the rare complications that we see in total knee replacements (infection, blood clots and other medical problems) occur even less frequently in partial knee replacements. In addition to blood thinners, rapid recovery protocols and early return to activities have helped to reduce the risk of blood clots. Arthritis in other parts of the knee can occur in a small percentage of patients over time.