Partial Knee Replacement

What is a partial or unicondylar knee replacement?

In some patients arthritis of the knee affects predominantly one portion of the knee joint hence allowing for onlythat portion of the joint to be replaced. Not all patients can have this operation and the suitability will be determined when you see me in clinic. It depends upon numerous factors including the location of pain, the range of movement, the location of arthritis on the x-ray and the integrity of the ligaments. I use the Oxford partial knee replacement in my practice.

What is the benefit of a partial knee replacement?

The operation is a less invasive procedure done through a smaller incision. The post-operative recovery is faster because of this. The knee functions better because all the ligaments and 2/3rd of the native joint is preserved leading to better range of movement and a more natural feeling joint. This results in higher levels of satisfaction with a partial knee compared to a total knee replacement. The other advantages are less blood loss and less medical complication after surgery. The operation also lends itself to day case surgery or a shorter length of stay in the hospital.

Should you have a partial knee replacement?

The decision to offer any kind of knee replacement is based on a shared decision-making at your consultation taking into consideration all the pros and cons of each procedure. As previously mentioned the suitability of a partial knee replacement is dependent on the location of pain and arthritis on the x-ray. The preoperative range of movement and the integrity of ligaments will play a key role. One potential advantage of having a partial knee replacement if suitable is that it will defer the need for a total knee replacement by many years.

What is the success rate of a partial knee replacement?

Unicompartmental or partial knee replacement is very successful in relieving knee pain and restoring joint function. Like total knee replacements 85% of patients are very satisfied with the procedure. Of the remainder, 10% maybe neither better nor worse and 5% may be worse due to persistent pain or complications. According to the National joint registry the revision rate for the Oxford cementless partial knee replacementat 10 years is 5.9% which means approximately 94% are lasting 10 years. The common causes of failure are progression of arthritis, loosening and wear of the implant and dislocations of the bearing. If these do happen most often the procedure is a straightforward conversion to a total knee replacement. Occasionally an augment is required on the inner side of the knee if there is loss of bone stock.

What are the risks of the operation?

Fortunately partial knee replacements have infrequent medical complications. The surgical risks include infection, deep vein thrombosis, pulmonary embolism, nerve and vessel damage, fracture, dislocation, persistent pain, stiffness, numbness adjacent to the scar, pain on kneeling, loosening and wear requiring a revision in the long term, anaesthetic and mortality risks. There are many measures undertaken to reduce these risks to you for example the use of clean air theatres, antibiotics and antithrombotic medication perioperatively. Surgical precision and careful handling of tissues during surgery to minimise pain and improve long term outcomes.

How to get the best partial knee replacement?

There is no such thing as the best knee replacement. There are many different partial knee replacements that are used by surgeons and the Oxford partial knee is one of the leading and most frequently used worldwide. However as partial knee replacements are less frequently performed compared to total knee replacements it is essential for you to identify a surgeon who performs this procedure frequently. You may find this information on the national joint registry surgeon profile. In my practice 40% of the knee replacements I perform are partial knee replacements.