What is knee replacement?

In knee replacement surgery, the bone surfaces and cartilage that have been damaged are removed and replaced with artificial surfaces, called implants, made of metal and a very durable plastic material.

Partial knee replacement

Unicompartmental knee replacement

For some people with osteoarthritis, the joint damage is limited to only one portion of their knee. If you experience pain only on one side, or compartment, of your knee, your doctor may diagnose you with unicompartmental osteoarthritis. When this is the case, your surgeon may prescribe unicompartmental knee replacement. This partial knee replacement procedure preserves the healthy side of your knee. Only one side of the joint – the diseased portion – is replaced, leaving the healthy portion untouched.

A successful partial knee replacement may relieve pain and preserve more of your natural anatomy. It may delay or, in some cases, prevent a more extensive total knee replacement.1-2

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Patella-femoral knee replacement 

If you experience pain under the knee cap, your doctor may diagnose you with patella-femoral osteoarthritis and recommend another type of partial knee replacement called patella-femoral knee replacement. This procedure replaces just the diseased portions of your knee, the femur and patella, while preserving the undamaged portion of your knee and your tibia.

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Total knee replacement

Total knee replacement

For most people, the joint damage affects all of the surfaces in their knee. A total knee replacement is usually considered when the surfaces on both sides of the bones, as well as the underside of the patella, are significantly damaged.

In total knee replacement surgery, the surface of the thighbone (femur) is replaced with a contoured metal piece. The surface of the shinbone (tibia) is typically replaced with a flat metal piece and a smooth plastic piece that serves as cartilage. The undersurface of the kneecap may also be replaced with an implant made of plastic or a combination of metal and plastic.

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Is it time for knee replacement?


That’s a question you and your doctor will have to answer together. However, when non-surgical treatments aren’t providing enough relief for you to enjoy life the way you’d like, the time may be right to consider knee replacement surgery.

Here are some signs to consider when deciding if it may be time for a knee replacement:

  • You have pain that keeps you awake or awakens you at night

  • You have pain that limits activities necessary to go about your daily routine, such as getting up from a chair or climbing stairs

  • You have pain that limits activities that give you pleasure, such as walking for exercise, traveling or shopping

  • You have tried other treatments for a reasonable period of time, and you still have persistent pain

You and your doctor must consider many other factors prior to surgery, including age, overall health and bone density. The list above can help you understand when you may begin to consider joint replacement surgery. Every surgical procedure has some risks and benefits. Your individual results will depend on personal circumstances, and recovery takes time.

Don’t wait too long for joint replacement surgery

Historically, patients were advised to delay joint replacement surgery as long as possible in order to avoid secondary operations when the artificial joints wore out.

More recently, a National Institutes of Health (NIH) Consensus Panel concluded that total knee replacement is extremely successful, resulting in “rapid and substantial improvement in the patient’s pain, functional status, and overall health-related quality of life in about 90% of patients.” 3

When your life is dictated by the limitations caused by your arthritic knee, the time has come to consider joint replacement.


What is it like to have knee replacement surgery?

When you and your surgeon have decided that it’s time for knee replacement surgery, there are likely many questions on your mind. This information is intended to provide you with an overview of what to typically expect before, during, and after surgery. Whether you are preparing for total or partial knee replacement, you can expect the process to be much the same. Every patient is unique and may have different needs and requirements, which should be discussed with your surgeon.

Before surgery

There are a number of tasks to complete before surgery day. Your surgeon usually schedules the procedure well in advance, giving you time to make necessary plans and arrangements.

Your surgeon may recommend a physical exam by a primary care physician to verify that your health allows you to proceed with surgery. Review with your primary care physician all of the medications you currently take. Your doctor may want to discuss your medications with your surgeon, or recommend that you discontinue certain medications that may increase the risk of bleeding during surgery. Your doctor may also suggest that you lose weight and begin an exercise program. If you smoke, speak candidly with your doctor about it. For most people, smoking is a serious risk before surgery because it diminishes blood circulation, which can delay the healing process.

Before surgery, remain as active as your health permits, and ask your doctor about starting an exercise program. Your doctor may suggest that you meet with a physical therapist to strengthen your muscles and maintain your range of motion. The more you can build upper body strength, the better prepared you will be for the use of a walker, crutches or cane. Getting accustomed to an exercise routine before surgery can make it easier to maintain physical therapy after you return home.

During surgery

On the day of surgery, a small intravenous (IV) tube will be inserted into a vein in your arm. The tube will be used to administer antibiotics, pain medication, and liquid nutrition during and after your surgery. You will then be taken to the operating room and given anesthesia.

The procedure is performed through an incision on your knee joint. The length and exact location of the incision will vary depending on your specific situation. The surgeon then removes the damaged bone surfaces and places the final implants, securing them either by bone cement or by friction. After the implants are secured in place, the ligaments surrounding the knee may be adjusted for improved knee function, and the incision will be closed.

For some patients, a less-invasive approach may be sufficient to replace the joint.

This may utilize a smaller incision and less or no cutting of key muscles and tissues.

After surgery

After the surgery is complete, you will be taken to the recovery room. As the anesthesia wears off, you will slowly regain consciousness and will be closely monitored. Your knee may be wrapped in a cooling pad to reduce swelling and pain, and your legs and feet may be covered with plastic wrappings to promote circulation. Once you are fully awake, you will be moved to your room or another location for further recovery until discharge. Approximately one or two hours after you leave the recovery area, you may begin gentle rehabilitation to strengthen your muscles and regain your range of motion.

What can I expect after surgery?

Recovery after surgery is different for every patient and is influenced by a variety of factors. Following surgery, you will begin a rehabilitation program prescribed by your surgeon to help strengthen the muscles around your new knee and regain your range of motion. You will also learn how to protect your new knee while doing daily activities.

As soon as possible, usually within the next 24 hours, your physical therapist will help you start walking a few steps at a time with the aid of a walker. Before you are dismissed from the hospital, a physical therapist will guide you through activities such as getting into and out of bed, standing and walking with crutches or a walker, and maneuvering stairs. Your therapist and doctor will also review the precautions you should take with your new knee.

After about 1 to 7 days, or when your surgeon determines that you have recovered sufficiently, you will be discharged. You may be transferred to a rehabilitation facility for a few more days, as determined by your surgeon. Upon returning to your home, you will need to continue taking your medications and exercising as directed by your surgeon or physical therapist.

Recovery varies greatly based on individual factors. In most cases, successful knee replacement will relieve your pain and stiffness, and allow you to resume many of your normal daily activities. But even after you have fully recovered from your surgery, you will still have some restrictions. Normal daily activities do not include contact sports or activities that put excessive strain on your knees. 

Important note: It is important that you closely follow the rehabilitation and physical therapy program or other instructions prescribed by your medical care professionals.  None of the information contained on this website is intended to substitute or supersede your doctor’s professional medical advice and instructions.



Compared to total knee replacement.

  1. Hopper, PG.,Leach, WJ. Participation in sporting activities following total knee replacement: total versus unicompartmental. Knee Surgery Sports Traumatology Arthroscopy.2008.16:973-979
  2. Hall et al. Unicompartmental Knee Arthroplasty (Alias Uni-Knee)-An Overview with Nursing Implications. Orthopedic Nursing. 2004; 23(3):163-171
  3. NIH Consensus Statement on Total Knee Replacement. NIH Consens State Sci Statements. 2003;20:1-32.
  4. Timing of total joint replacement affects clinical outcomes among patients with osteoarthritis of the hip or knee. Arthritis Rheum. 2002 Dec;46(12):3327-30.

Important note: The person depicted in this advertisement is a model and not an actual recipient of Zimmer Biomet products. Results are not necessarily typical, indicative, or representative of all recipient patients. Results may vary.  Not all patients are candidates for this product and/or procedure.  Only a medical professional can determine the treatment appropriate for your specific condition.  Appropriate post-operative activities will differ from patient to patient.   Talk to your surgeon about whether joint replacement is right for you and the risks of the procedure, including the risk of implant wear or failure.  All content herein is protected by copyright, trademarks and other intellectual property rights owned by or licensed to Zimmer Biomet or its affiliates unless otherwise indicated, and must not be redistributed, duplicated or disclosed, in whole or in part, without the express written consent of Zimmer Biomet.