Queen's Medical Center POB1, 1380 Lusitana Street, Suite 808, Honolulu, HI 96813

Partial Knee Replacement Surgery

A more natural feeling knee

What is a partial knee replacement?

Partial knee replacements (unicompartmental knee replacements) are a type of knee replacement that only replaces the arthritic part of the knee.  Patients with a partial knee recover from their surgery faster and are more likely to have a knee that feels like a normal knee compared to a total knee replacement.

Partial knee replacements only replace the part of the knee that is arthritic.  In a total knee replacement, there are two ligaments that are normally removed - the anterior cruciate ligament and the posterior cruciate ligaments.  In addition, partial knee replacements allow you to keep the good cartilage that is in your knee. Unlike a traditional knee replacement, partial knees are considered a resurfacing.


What are the different types of partial knee replacements?

There are a few different types of partial knees.  The inside of your knee is considered the "medial compartment". Meanwhile the outside of the knee is the "lateral compartment". The part underneath the knee cap is called the "patellofemoral compartment". Each of these compartments can be replaced indepenently with a lateral, medial or patellofemoral replacement. Sometimes two compartments can be replaced, a "bicompartmental replacement"


Who is a candidate for a partial knee replacement


Recovery after a Partial Knee Replacement

Frequently Asked Questions

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Is Partial Knee Replacement surgery right for you?

Partial knee replacements are a good option for you if you have severe knee pain that does not improve with conservative treatment. In addition, you should have arthritis isolated to only location. If you have arthritis in more than one compartment, having a partial knee replacement may lead to an early revision surgery.  You should consider surgery when you have problems in certain areas of your life secondary to your knee pain such as:

  • Problems with activities of daily living: household chores or grocery shopping
  • Performing activities you enjoy: long walks, golf, riding a bike, or gardening
  • Occupational activities: inability to perform functions of your jobs
  • Enjoyment of family: Pain associated with playing with your grandchildren or activities with your spouse

I have arthritis, but I was told I was not a candidate for a partial knee replacement

If you have severe deformity, loss of ACL function, inflammatory arthritis, or severe osteoarthritis, a partial knee replacement may lead to a high chance of failure of your partial knee replacement and likely future revision knee replacement.


Patients who undergo a partial knee replacement have:

  • Smaller incision
  • Less pain
  • Less blood loss
  • Quicker recovery from the surgery


A partial knee replacement only resurfaces part of your knee. Some patients can have excess pressure placed on their un-resurfaced portion of their knee. This increase in pressure can lead to degenerative wear in the areas of the knee that was not replaced. This increase in wear leads to further arthritis of the joint. The best way to prevent this is by better placement of components using robotic-assistance. Talk with Dr. Morton to see if you are a candidate for a partial knee replacement. Dr. Morton can help explain why you might not be a good candidate for a partial knee replacement.

Reasons to avoid a  partial knee replacement:

  • Deformity
  • Inflammatory arthritis
  • Severe ligament damage

Recovery after Partial Knee Replacement

After your partial knee replacement, you will begin walking on the day of surgery after you recover from anesthesia. Many patients are able to go home after surgery. Your physical therapist will assist you in beginning to walk again. Often you will have pain while you are recovering and you will have to work on recovering your muscle strength. You may require a walker or a cane to get around for the first couple of months after surgery. During your surgery, we provide multiple modes of anesthesia to reduce your pain including nerve blocks, intra-operative injections, and a low-narcotic pain medication regimen.


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Many patients are able to walk normally 2 - 3 weeks after surgery. Most patients are able to return to many of your activities by 6 weeks after surgery.  Over the course of a year, you will continuously gain benefits from your knee replacement. Sometimes it may take 2 years to get the full benefit of your new knee.

The goal of your partial knee replacement is to give you the best opportunity to have a normal feeling knee that will allow you to return to activities that you enjoy such as long walks, dancing, golfing, gardening, and biking. A partial knee replacement has been performed for many years with an excellent track record for improving quality of life, returning patients to their independence, and reducing pain.

Have Realistic Expectations

Unfortunately, a knee replacement may not solve all of your knee problems. More than 90% of patients who undergo a partial knee replacement have a dramatic improvement in their knee pain. This gives patients the ability to return to a normal lifestyle and perform everyday activities. Over time, the plastic component in your partial knee replacement can wear out.  Increased weight, or high levels of impact activity may speed up this wear and cause problems with your knee.  The American Association of Hip and Knee Surgeons advise patients to avoid high impact activities such as running, jogging, jumping, or other high-impact activities with a knee replacement.


Despite the technological and medical advancements that we have made, there are still risks with partial knee replacement surgery. Risks include:

  • Infection
  • Blood loss
  • Blood clots
  • Wear of non-arthritic compartment
  • Fracture
  • Implant loosening
  • Knee stiffness
  • Nerve or blood vessel damage

Dr. Morton will do his best to avoid complications. Please discuss any concerns that you may have with him prior to your surgery.

Trying to figure out between a partial and a total knee replacement? Learn more here.


Frequently Asked Questions about Robotic Joint Replacement (FAQ)

What is the normal recovery time for a partial knee replacement?

Recovery from a partial knee replacement is generally faster compared to a total knee replacement. Partial knee replacements usually recover between 4 and 10 weeks. Total knee replacements can take between 8 to 12 weeks for a recovery.

What can I expect with a partial knee replacement?

Comparatively, there is less surgery associated with a partial knee replacement. This results in less blood loss, less pain, and quicker recovery. Patients are generally able to return home on the same day of surgery. You are able to shower right away. After about 6 weeks, most patients are able to return to many of their normal activities.

Who is a candidate for a partial knee replacement?

Partial knee replacements are a good surgical option for patients who have isolate osteoarthritis to only one compartment. The knee is made of three compartments - medial, lateral, and patellofemoral. Partial knee replacements in patients with arthritis in more than one compartment are at high risk of failure after a partial knee replacement.

How long does a partial knee replacement last?

Partial knee replacements that are done for the right reasons can last a lifetime. Patients who are heavier, have a higher activity level, or have arthritis in other areas of their knee are at a higher risk for failure. At 10 years, 90% of partial knees done with historical techniques are still functioning well. Using robotic assistance, surgeries are able to have their implants placed in better positions, and the longevity approaches that of total knees, while maintaining the improved kinematics from a partial knee.

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Meet Dr. Paul N. Morton, MD

Dr. Paul N. Morton, MD is a fellowship-trained orthopedic surgeon in hip and knee surgery, specializing in robotic joint replacements, complex joint reconstruction, sports injuries, and trauma. Reach out to him to learn more about treatment options for your problem.

Written By: Dr. Paul N. Morton, MD


Post Published on October 17, 2018