Purpose of Knee Replacement Surgery

Knee replacement surgery—also called knee arthroplasty—is an elective surgery performed by an orthopedic surgeon in a hospital. The surgery, which is most commonly performed in patients with knee osteoarthritis, involves removing the damaged parts of the knee joint and replacing it with an implant made of metal and plastic.

Doctor and patient having a discussion in an exam room
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Diagnoses Related to Knee Replacement Surgery

Knee replacement surgery is performed in patients with severe knee arthritis, usually osteoarthritis. 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 undergoing knee replacement surgery for arthritis, their knee is so damaged, 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 non-surgical therapies often include a combination of the following:

Besides arthritis, other knee conditions that may require a knee replacement include:

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


There is 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.

This surgery, while effective and long-lasting, does involve risks, as well as a prolonged recovery and rehabilitation process. Therefore, many people struggle to decide if and when they should proceed with it.

Some people want their knee replaced at the first hint of knowing that might be an option, while others want to hang in as long as possible, despite the level of symptoms they may be experiencing. Many people know friends or family members who have had the surgery and often worry about another individual's particular experience.

Due to these complicated issues and because of the lack of formal criteria, it's common to struggle to make a decision.

Here are some potential signs to help you decide if the time is right for knee replacement surgery.

Signs You May Be Ready

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

Tests and Labs

While the list above is a good start to considering knee replacement surgery, your surgeon will need to perform a thorough evaluation before confirming surgery is right for you.

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

  • A physical examination: Your surgeon will access 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 ensure a problem there is not the source of or 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 a 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 access your health risks, or if you have 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

On a final note—while knee replacement is generally considered a "last resort" treatment for knee arthritis, this does not mean you need to crawl into your surgeon's office just to be considered for this procedure. 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.

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