Partial vs. Total Knee Replacement Surgery

The Differences Have to Do With the Affected Knee Compartments

Total knee replacement, also known as total knee arthroplasty, is a highly successful surgical procedure. It is not the only surgical treatment option for knee osteoarthritis, though. Some patients are candidates for partial knee replacement, also known as unicompartmental knee arthroplasty.

X-ray showing total knee replacement
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Difference Between Total and Partial Knee Replacement

The knee has three compartments—the medial compartment (inside aspect of the knee), the lateral compartment (outside of the knee) and the patellofemoral compartment (in front of the knee). In some knee osteoarthritis patients, only one compartment of the knee is affected—usually the medial compartment. The lateral compartment can be affected, but it is less common.

A partial or unicondylar knee replacement, as its name suggests, replaces only the affected compartment of the knee. On the other hand, a total knee replacement involves the replacement of all three compartments of the knee.

While just one compartment is replaced during partial knee replacement, anterior and posterior cruciate ligaments are preserved. The ligaments are removed in a total knee replacement. Suffice it to say, with a partial knee replacement, more of your own body structure remains intact.

Benefits and Risks With Partial Knee Replacement

There are benefits to having a partial knee replacement as compared to a total knee replacement. The same complications are possible with both surgical procedures: loosening, infection, nerve injury, fracture of the bone and more.

Benefits
  • Less bone and soft tissue dissection

  • Less blood loss

  • Fewer complications

  • Faster recovery of range of motion

  • Better range of motion overall

Risks
  • A higher revision (repeat or redo) rate for partial knee replacement than total knee replacement

  • Potentially worse function after revision of partial knee replacement than total knee replacement

  • Revisions can be more complicated than primary surgeries

Good and Bad Candidates for Partial Knee Replacement

In 1998, two doctors (Drs. Scott and Kozinn) established criteria for determining which patients were good candidates for partial knee replacement. The ideal patient:

  • Older than 60 years old
  • Less than 180 lbs
  • Less active
  • Has good range of motion before surgery
  • Has minimal deformity

Patients with inflammatory types of arthritis, such as rheumatoid arthritis, are not regarded as good candidates for partial knee replacement. With inflammatory arthritis, more than one compartment is usually involved.

Recovery and Success Rates

Recovery times vary per person and also depends on general health. Knee replacement surgeries are typically successful, with at least 90% offering pain relief and about 90% of total knee replacements still functional after 20 years.

The data on partial knee replacements is more limited and sometimes complicated by surgeries in those who were not great candidates. Studies do suggest that about 90% of partial knee replacements are functional after 10 years and approximately 70% are functional (no additional surgeries) after 25 years.

Walking and Other Low-Impact Activities

Physical therapy is an important part of the recovery process and can help in restoring mobility for any type of knee replacement.

Some level of walking with assistance is usually possible after a total knee replacement surgery and many can walk on their own within a few weeks. A full return to unlimited low impact activities such as walking, biking, and swimming are often possible within a few months. It may take six months to one year to reach maximum strength and mobility.

Recovery tends to be faster for a partial knee replacements with a full return to activities possible within three to six weeks. However, the majority of knee replacement candidates have more than one area that is damage or diseased, so a total knee replacement is recommended for the best outcomes.

Complications

Serious complications, such as a joint infection, after surgery occur in about 2% of those who have a total knee replacement and may prolong or limit recovery. In some cases, the complication may be so severe that the implant may need to be removed and replaced.

Serious complications are even more uncommon for partial knee replacements, with infections occurring in less 1% of patients.

Bottom Line

There have been improvements in the design of unicompartmental prostheses over the years. Having a surgeon experienced in working with partial knee replacements is a plus too. Ultimately, a successful outcome depends on having the right patient for the procedure. It is estimated, though, that only 6% to 10% of patients are suitable candidates for partial knee replacement.

Frequently Asked Questions

  • Is a total or partial knee replacement better?

    It depends. A partial knee replacement is less invasive and recovery tends to be much quicker. However, if two or more parts of the knee are damaged, a total knee replacement offers the best outcomes.

  • Who is a candidate for a partial knee replacement?

    Those with damage to only one part of the knee joint. The surgery replaces the damaged or worn out portion only and leaves the other healthy tissue and bone.

  • What are the pros and cons of a partial knee replacement?

    Pros: Recovery tends to be faster and less painful than a total knee replacement and there may be better range of motion and a more natural feel to the knee. There is also a slightly lower risk of serious complications, such as infections or blood clots.

    Cons: Many people are not good candidates for a partial knee replacement. If damage occurs to the other parts of the knee joint, additional surgeries, such as a conversion to a total knee replacement, may be needed later on.

  • What is the success rate of a partial knee replacement?

    Studies show that about 90% of partial knee replacements are still functional at least 10 years after surgery, including in patients under age 60. There is limited data beyond this, but registries of those who've had knee surgeries suggest about 70% of partial knee replacements are still functional 25 years after surgery.

  • How soon can you walk after a partial knee replacement?

    You can put full weight on your knee following the surgery and should be able to walk with assistance, such as walker or crutches, within a few days. Regular walking without assistance is typically possible within three to four weeks.

  • What can you not do after a partial knee replacement?

    High-impact activities, such as running, typically need to be avoided.

  • How long does it take to recover from total knee replacement?

    About three months to resume most activities. It may take about six months to one year to reach maximum strength and mobility.

  • Is total knee replacement a major surgery?

    Yes, it's a major surgery. Serious complications are rare but sometimes occur.

  • Is partial knee replacement a good idea?

    It depends on whether or not you are a good candidate for the surgery and your individual medical history. Discuss options with your healthcare provider.

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11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Partial Knee Replacement. Conditions and Treatments. Hospital for Special Surgery. Friedrich Boettner, MD. 3/27/2008.