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:

Rheumatoid arthritis Post-traumatic arthritis (arthritis that results from a knee injury) Psoriatic arthritis Lupus arthritis Juvenile idiopathic arthritis (rare)

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:

Walking program Physical therapy Weight loss (if overweight or obese) Nonsteroidal anti-inflammatory drugs (NSAIDs) Injections into the knee joint (typically, a corticosteroid) Wearing a knee brace

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

Criteria

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 nightKnee 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 painA 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.

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:

Electrocardiogram (ECG) Chest X-ray Urinalysis Blood tests, such as a complete blood count (CBC) and basic metabolic panel

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.