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There tends be a lot of questions and often misconceptions around partial knee replacement. Is it as good as a total knee replacement? Why get a partial knee replacement when I can get a full replacement?  Some patients are skeptical because they think a partial replacement may only be a temporary solution.  If I get a partial replacement now, will I need to get a full replacement later?  Friends and family say why not just do the whole thing?   This is based on misunderstanding of what we are doing and why. For the right patient, a partial knee replacement is the total solution to a partial problem, and people who get partial knee replacements tend to be the most satisfied patients.

The History of Partial Knee Replacement

Partial knee replacements are not new.  They have been around since the 1970’s, however, results from the earliest partial knees weren’t as good as total knees at the time and they developed a bad reputation 30 or 40 years ago. There were several reasons for this.   First, the early implants and instruments used to put them in were not technologically advanced,  Second, because surgeons hadn’t quite perfected the surgical technique, and third, and probably most importantly, surgeons didn’t know how to choose the ideal candidate for a partial knee replacement.  Partial knee replacements, therefore, got a bad reputation with surgeons who tried the procedure with mixed success. Over the last couple decades, things have changed. The implants and surgical instruments are markedly improved and well-studied, the surgical techniques are refined and exacting, and we know now, based on decades of experience who is and who isn’t a good candidate for a partial knee.  In fact, modern data on partial knee replacements is excellent; Studies show that partial knee replacement patients tend to have higher satisfaction and better function than total knee replacement patients.  Additionally, several studies show that the longevity of partial knee replacements is quite similar to total knee replacement¹.

Even though the modern data is excellent today, not all joint replacement surgeons have experience doing partial replacements, and many respected surgeons who were not trained with partial knees are biased by older techniques and outdated studies.

The Right Patient and the Right Surgeon

Not all patients are candidates for partial knees.  In order to have a successful partial knee replacement, we must select the correct patient for this type of surgery. Additionally, it is also very important to have a surgeon who specializes in this type of procedure.

The right patient for a partial knee replacement is one who has truly isolated arthritis in one of the three compartments of the knee. Arthritis that occurs in only one compartment of the knee is actually quite common—perhaps as high as 40 or more percent of patients. Arthritis occurs in only one compartment for a variety of reasons. Some examples:

• Congenital or genetic predispositions such as bow leggedness or knock knees – may subject the inside or outside portion of the joint to abnormal stress and wear over time, while leaving the rest of the knee normal
• Traumatic injury to one compartment of the knee (such as a meniscus tear), which leads to isolated cartilage damage to that part of the knee only.
• Osteonecrosis, where one specific part of the bone dies or damaged, is another condition that may be an indication for a partial knee replacement.

X-rays, physical exam, and a careful patient history are used to determine how much arthritis is present and which compartment or compartments are involved. In rare instances, MRI or other studies can be helpful. The doctor will usually make the final decision in the operating room.  That is if during surgery the knee is opened and it is discovered that the arthritis is NOT isolated in one compartment only, then a total knee replacement can be done instead.

The benefits of a partial knee replacement

Patients who have partial knee replacements are some of the happiest!  In general, partial knee replacements feel more natural and have better function as compared to total knee replacements.  Often these patients may forget which knee was operated on over time. Some of the benefits of a partial knee replacement over a total knee replacement:

• It is generally a faster, easier recovery with less pain and less downtime
• It tends to feel more like a natural knee – it is often known as a forgotten knee – they feel so natural that patients don’t think about it anymore.
• There is less risk for infection, blood clots, and stiffness.

Because this procedure is less painful, patients are often off pain medications within a couple days of their surgery. They are usually not requiring a cane or walker within a week. People are also often pleasantly surprised by how reasonable the recovery is.

As a surgeon it is our philosophy is do the minimum we can do to make the patient whole – whether that is operative or not.  If it is operative – we want to do the minimum needed to have a result that brings the patient back to 100%. In many cases the perfect solution is a partial knee replacement: “a total solution to a partial problem!”

Dr Jared Foran is a joint replacement surgeon at Panorama Orthopedics & Spine Center.  He performs more than 500 hip and knee replacements each year.  His specializes in minimally invasive and partial knee replacement procedures.