Purpose of Knee Replacement Surgery

Knee replacement surgery (knee arthroplasty) is an elective surgery done to reduce pain, stiffness, and disability caused by damage to the knee joint when conservative treatments have failed to provide symptom relief. Most commonly done to treat knee osteoarthritis, knee replacement surgery involves removing the compromised parts of the knee joint and implanting a prosthesis made of metal and plastic.

Woman bracing herself on counter due to knee pain
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Diagnoses Related to Knee Replacement Surgery

Knee replacement surgery isn't appropriate for all instances of knee arthritis, but it may be helpful in severe cases. Knee osteoarthritis develops when the smooth cartilage that normally cushions the knee joint wears away. This condition is most common in people age 50 years or older, but it can occur in younger individuals as well.

In addition to osteoarthritis, other types of knee arthritis that may warrant a knee replacement include:

Patients who undergo knee replacement surgery for arthritis have such damage to their knee that they often have trouble performing daily activities. They also suffer from symptoms of severe, constant, and unpredictable knee pain and stiffness that cannot be adequately controlled with various nonsurgical therapies.

These often include a combination of the following, which will typically be tried—and found to be ineffective—before surgery is considered:

Besides arthritis, other knee conditions that may prompt the need for a knee replacement include:

  • A tumor of the knee bone
  • Knee osteonecrosis
  • Congenital (present at birth) knee deformities


There are no set-in-stone medical guidelines for determining who is a candidate for knee replacement surgery and when the right time to undergo the operation is.

You may be ready for a knee replacement if you have:

  • Moderate-to-severe knee pain while resting and/or that keeps you awake at night
  • Knee pain that limits activities necessary to go about your daily routine (such as getting up from a chair or climbing stairs)
  • Knee pain that limits activities that give you pleasure (such as walking for exercise, traveling, or shopping)
  • Tried other treatments and still have persistent and/or severe knee pain
  • A knee deformity, such as bowing in or out of your knee

Your orthopedist can help guide you (and will ultimately be the one to clear you for the procedure), but the decision to proceed—and if so, when—is ultimately up to you.

Some people want their knee replaced as soon as they learn that surgery is an option for them, but others find giving the green light more difficult—even choosing to postpone surgery as long as possible despite the level of symptoms they may be experiencing.

This can be for a variety of reasons. Some may know someone who had the surgery and a challenging post-operative period, and worry that the same is in store for them. Others may worry about the invasiveness of the surgery or potential complications.

Take the time you need to consider and commit to what having this surgery means. Knee replacement, while effective and long-lasting, does involve risks, as well as a prolonged recovery and rehabilitation process. You need to not only be physically ready for the surgery, but mentally prepared for what comes after it as well.

Tests and Labs

Your surgeon will need to perform a thorough evaluation to confirm that surgery is both a safe and appropriate option in your case.

Besides a comprehensive medical history, other exams and tests that will be performed include:

  • A physical examination: Your surgeon will assess the strength and range of motion of your knee, as well as joint stability and overall leg alignment. They will also evaluate your hip joint to rule out that a problem there is not the source of/contributing to your knee pain.
  • X-rays: Images of your knee will give your surgeon an idea of the severity of arthritis in your knee. In addition to an X-ray, your surgeon may also recommend magnetic resonance imaging (MRI) of your knee.

Once your surgery is scheduled, you may need to undergo the following tests for medical clearance:

Additionally, you may need to see various specialists to assess your health risks, including underlying medical problems. For example, you may have to see a cardiologist to evaluate your pre-operative cardiovascular risk. If you have peripheral arterial disease, your surgeon may ask that you consult with a vascular surgeon before surgery.

A dental evaluation may also be required. Since dental procedures (especially major ones like a tooth extraction) may allow bacteria to enter your bloodstream, it's important to complete your dental work at least two weeks prior to your scheduled surgery date.

A Word From Verywell

While knee replacement is generally considered a last-resort treatment for knee arthritis, this does not mean you need to be hobbling around in excruciating pain just to be considered a candidate. The goal is to try simpler, less-risky treatments first, and if these are not effective, consider a knee replacement when the surgery is most likely to benefit you.

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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By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.