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Replacing a Worn Knee Joint

You use your knee every time you take a step. Because of this, living with a worn or injured knee joint can be painful and frustrating. Even simple things, such as squatting to pick up the morning paper, may cause pain. But you don't have to live this way. In many cases, an orthopaedic surgeon (a doctor who treats bone and joint problems) can replace the damaged knee joint. The surgery is safe and effective. For many people, having a total knee replacement means a return to pain free movement.

A Problem Knee

No matter what your age, a problem with the knee joint may keep you from activities you enjoy. Pain and stiffness may even limit the daily tasks you can do. Problems with the knee joint tend to build up over time. Your knee pain may be caused by any of the following:

  • A bad injury that did not heal properly
  • A chronic illness
  • Wear and tear from years of constant use

Surgery Can Help

You may not have to live with knee pain for the rest of your life. Total knee replacement surgery almost always reduces joint pain. During this surgery, your damaged knee joint is replaced with an artificial joint (called a prosthesis). Surgery can't make you young again, but it can bring real benefits.

Benefits of Knee Replacement

After a total knee replacement, you can look forward to moving more easily. Most people gain all of the benefits listed below. Knee replacement surgery almost always:

  • Stops or greatly reduces joint pain. Even the pain from surgery should go away within weeks.
  • Increases leg strength. Without knee pain, you'll be able to use your legs more. This will build up your muscles.
  • Improves your quality of life by allowing you to do daily tasks and low-impact activities in greater comfort.
  • Provides years of easier movement. Most total knee replacements last for many years.

How the Knee Works

A healthy knee bends easily. The joint absorbs stress and glides smoothly. This allows you to walk, squat, and turn without pain. But when the knee is damaged, the joint may lose its ability to cushion stress. You may feel pain during movement. Sometimes a damaged knee joint will swell and hurt even when you are at rest.

A Healthy Knee

The knee is a hinge joint, formed where the thighbone and shinbone meet. When the knee is healthy, the joint moves freely: This is because the joint is covered with slippery tissue and powered by large muscles.

  • Cartilage is a layer of smooth, soft tissue. It covers the ends of the thighbone and shinbone, and it lines the underside of the kneecap. Healthy cartilage absorbs stress and allows the knee to glide easily.
  • Ligaments are another type of soft tissue. They hold the bones of the joint together.
  • Muscles power the knee and leg for movement.
  • Tendons attach the muscles to the bones.

A Damaged Knee

When one or more parts of the knee are damaged, joint movement suffers. Over time, cartilage starts to crack or wear away. Because cartilage cannot fully repair itself, the damage may keep increasing. At first, your knee may just be a little stiff. But as the bones of the joint begin rubbing together, you're likely to feel pain.


Years of normal use can cause cartilage to crack and wear away (osteoarthritis). As exposed bones rub together, they become rough and pitted. The joint grinds. Being overweight or having an alignment problem, such as knocked or bowed knees, puts extra force on the joint. This may speed up the damage.

Inflammatory Arthritis

A chronic disease, such as rheumatoid arthritis or gout, can cause swelling and heat (inflammation) in the joint lining. As the disease progresses, cartilage may be worn away and the joint may stiffen.


A bad fall or blow to the knee can injure the joint. If the injury does not heal properly; extra force may be placed on the joint. Over time, this can cause the cartilage to wear away (traumatic arthritis).

Is Surgery Right for You?

Your doctor may have tried to reduce your knee pain with medications. You may even have had minor surgery (arthroscopy) to help treat the problem. But if this didn't help enough, total joint replacement might be right for you. To find out, your surgeon will evaluate your knee joint. You'll have a full physical exam and x-rays. When forming a treatment plan, your surgeon thinks about how surgery can best benefit you over your lifetime.

Your Medical History

Your surgeon may start by asking you about any past medical problems. He or she is likely to ask where your knee hurts and what makes the pain worse. Tell your surgeon about any other joint problems or any injuries to your knee or leg. If surgery seems likely, be sure to mention any past problems with anesthesia or bleeding.

Your Physical Exam

Your surgeon will fully examine your knee. He or shee will feel for any swelling around the joint.  Nearby muscules and tendons may also be checked.  The joint itself will be tested for strength, stability, and range of motion.  You may also be checked for other conditions, such as a pinched nerve, which could cause pain in or near the knee.


X-rays will be taken to provide an image of your knee joint. An x-ray may show changes in the size and shape of the joint. A buildup of bone (bone spur), a cyst, or pitting in the bone may also show up. These problems often form where cartilage has worn away. X-rays also help your surgeon plan your knee replacement. He or she may use x-rays to decide exactly where in the bone to place the prosthesis.

Your Treatment Plan

Your surgeon uses the results of your exam and x-rays to form a treatment plan that is right for you. Depending on your age and the amount of damage to your knee, surgery may offer the best answer to your problem. A total knee replacement lasts many years, and it can often be repeated if the first prosthesis wears out. But if you are still fairly young, your surgeon may suggest delaying surgery. In this case, medications or arthroscopy may help control your symptoms until the time is right for joint replacement.

The Surgical Procedure

When the surgical team is ready, you'll be taken to the operating room. There you'll be given anesthesia. The anesthesia will help you sleep through surgery, or it will make you numb from the waist down. Then an incision is made on the front or side of your knee. Any damaged bone is cleaned away, and the new joint is put into place. The incision is closed with staples or stitches.

Preparing the Bone

All of the bone surfaces of the joint are shaped to hold the prosthesis. Then the parts of the prosthesis are put in place. At this point, your surgeon tests the fit and alignment of the prosthesis.

Joining the New Parts

If the prosthesis fits correctly, its parts are secured to the thighbone, kneecap, and shinbone. Then these parts are joined. Together they form the new joint.

In the Recovery Room

After surgery you'll be sent to the recovery room, also called the PACU (postanesthesia care unit). Your condition will be watched closely, and you'll be given pain medications. You may have a catheter (small tube) in your bladder and a drain in your hip. To keep your new joint stable, a foam wedge or pillows may be placed between your legs.

Returning to Activity

To build strength, practice walking every day. Try to do more each week. But be aware that some days you will feel better than others. You may be ready to drive or return to a desk job about a month after surgery. If you do more active work, you may need to wait 3 or 4 months before going back. Total knee replacement is a major surgery so don't be surprised if it takes a few months before you feel really good.