Overview

Knee replacement surgery replaces parts of injured or worn-out knee joints. This also is known as knee arthroplasty. During the surgery, damaged bone and cartilage are replaced with parts made of metal and plastic.

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Knee replacement surgery can help ease pain and make the knee work better. To decide whether a knee replacement is right for you, a surgeon checks your knee's range of motion, stability and strength. X-rays help show the extent of damage.

The right artificial joints and surgical techniques needed depend on many factors including age, weight, activity level, knee size and shape, and overall health.

Why it's done

The most common reason for knee replacement surgery is to ease pain caused by arthritis. People who need knee replacement surgery often have problems walking, climbing stairs and getting up out of chairs.

If only one part of the knee is damaged, surgeons often can replace just that part. This is called a partial knee replacement. If the entire joint needs to be replaced, the ends of the thighbone and shinbone are reshaped, and the entire joint is resurfaced. This is called a total knee replacement. The thighbone and shinbone are hard tubes that contain a soft center. The ends of the artificial parts are inserted into the softer central part of the bones.

Ligaments are bands of tissue that help hold joints together. If the knee's ligaments aren't strong enough to hold the joint together by themselves, the surgeon may choose implants that can be connected so they can't come apart.

Risks

Knee replacement surgery, like any surgery, carries risks. They include:

• Blood clots. Surgeons often recommend blood-thinning medicines to prevent this risk. The most common location for blood clots is in the leg. But they can travel to the lungs and become deadly.
• Nerve damage. Nerves in the area where the implant is placed can be injured. Nerve damage can cause numbness, weakness and pain.
• Infection. Infection can occur at the incision site or in the deeper tissue. Surgery is sometimes needed to treat an infection.

The implants used for knee replacements are durable, but they may loosen or become worn over time. If this happens, another surgery may be needed to replace the loose or worn parts.

How you prepare

Food and medicines

Your healthcare team might advise you to stop taking certain medicines and dietary supplements before your surgery. You'll likely be instructed not to eat anything after midnight the day of your surgery.

Prepare for your recovery

For several weeks after the procedure, you might need to use crutches or a walker, so arrange for them before your surgery. Make sure you have a ride home from the hospital and help with everyday tasks, such as cooking, bathing and doing laundry.

To make your home safer and easier to navigate during recovery, consider doing the following:

• Create a living space on one floor since climbing stairs can be difficult.
• Install safety bars or a secure handrail in your shower or bath.
• Secure stairway handrails.
• Get a stable chair with a firm seat cushion and back, and a footstool to elevate your leg.
• Arrange for a toilet seat riser with arms if you have a low toilet.
• Get a stable bench or chair for your shower.
• Remove loose rugs and cords.

What you can expect

When you check in for your surgery, you'll be asked to remove your clothes and put on a hospital gown. You'll be given either a spinal block, which numbs the lower half of your body, or a general anesthetic, which puts you into a sleep-like state.

Your surgeon also might inject a numbing medicine around nerves or in and around the joint to help block pain after your surgery.

During the procedure

Knee replacement surgery usually takes 1 to 2 hours. To perform the procedure, the surgeon:

• Makes an incision over the knee.
• Removes diseased and damaged bone and cartilage, leaving healthy bone intact.
• Implants the replacement parts into the thighbone, shinbone and kneecap.

After the procedure

After surgery, you'll rest in a recovery area for a short time. How long you stay in the hospital after surgery depends on your individual needs. Many people can go home the same day.

The risk of blood clots increases after knee replacement surgery. To prevent this complication, you may need to:

• Move early. You'll be encouraged to sit up and walk with crutches or a walker soon after surgery.
• Apply pressure. Both during and after surgery, you might wear elastic compression stockings or inflatable air sleeves on your lower legs. The air sleeves squeeze and release your legs. That helps keep blood from pooling in the leg veins, reducing the chance that clots will form.
• Take blood thinners. Your surgeon might prescribe an injected or oral blood thinner after surgery. Depending on how soon you walk, how active you are and your overall risk of blood clots, you might need blood thinners for several weeks after surgery.

You'll also likely be asked to do frequent breathing exercises and gradually increase your activity level. A physical therapist can show you how to exercise your new knee. After you leave the hospital, you'll likely continue physical therapy at home or at a center.

Results

For most people, knee replacement provides pain relief, improved mobility and a better quality of life. Most knee replacements can be expected to last at least 15 to 20 years.

After recovery, you can engage in various low-impact activities, such as walking, swimming, golfing or biking. But you should avoid higher impact activities, such as jogging, and sports that involve contact or jumping. Talk to your healthcare team about ways to stay active after knee replacement.

Clinical trials

Knee joint replacement

Knee joint replacement is a surgery to replace a knee joint with a man-made artificial joint. The artificial joint is called a prosthesis.

Damaged cartilage and bone are removed from the knee joint. Man-made pieces are then placed in the knee.

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These pieces may be placed in the following places in the knee joint:

• Lower end of the thigh bone -- This bone is called the femur. The replacement part is usually made of metal.
• Upper end of the shin bone, which is the large bone in your lower leg -- This bone is called the tibia. The replacement part is usually made from metal and strong plastic.
• Back side of your kneecap -- Your kneecap is called the patella. The replacement part is usually made from a strong plastic.

You will not feel any pain during the surgery. You will have one of these two types of anesthesia:

• General anesthesia -- This means you will be asleep and unable to feel pain.
• Regional (spinal or epidural) anesthesia -- Medicine is put into your spine to make you numb below your waist. You will also get medicine to make you sleepy. And you may get medicine that will make you forget about the procedure, even though you are not fully asleep.

After you receive anesthesia, your surgeon will make a cut over your knee to open it up. This cut is often 8 to 10 inches (20 to 25 centimeters) long. Then your surgeon will:

• Move your kneecap out of the way
• Cut the ends of your thigh bone and shin (lower leg) bone to fit the replacement part.
• Cut the underside of your kneecap to prepare it for the new pieces that will be attached there.
• Fasten the two parts of the prosthesis to your bones. One part will be attached to the end of your thigh bone and the other part will be attached to your shin bone. The pieces can be attached using bone cement or screws.
• Attach the underside of your kneecap. A special bone cement is used to attach this part.
• Repair (if needed) your muscles and tendons around the new joint and close the surgical cut.

The surgery takes about 2 hours.

Most artificial knees have both metal and plastic parts. Some surgeons now use different materials, including metal on metal, ceramic on ceramic, or ceramic on plastic.

Why the Procedure is Performed

The most common reason to have a knee joint replaced is to relieve severe arthritis pain. Your health care provider may recommend knee joint replacement if:

• You are having pain from knee arthritis that keeps you from sleeping or doing normal activities.
• You cannot walk and take care of yourself.
• Your knee pain has not improved with other treatment.
• You understand what surgery and recovery will be like.

Most of the time, knee joint replacement is done in people age 60 and older. Younger people who have a knee joint replaced may put extra stress on the artificial knee and cause it to wear out early and not last as long.

Before the Procedure

Always tell your provider what medicines you are taking, even medicines, supplements, or herbs you bought without a prescription.

During the 2 weeks before your surgery:

• Prepare your home for when you leave the hospital.
• One to two weeks before surgery, you may be asked to stop taking medicines that make it harder for your blood to clot. These include aspirin, ibuprofen (Advil, Motrin), naproxen (Naprosyn, Aleve), blood thinners such as warfarin (Coumadin), or clopidogrel (Plavix), and other medicines (such as Eliquis or Xarelto).
• You may also need to stop taking medicines that can make your body more likely to get an infection. These include methotrexate, etanercept (Enbrel), or other medicines that suppress your immune system. Make sure you ask your providers when it is safe to resume taking these medicines.
• Ask your surgeon which medicines you should still take on the day of your surgery.
• If you have diabetes, heart disease, or other medical conditions, your surgeon may ask you to see the provider who treats you for these conditions to see if it is safe for you to have the surgery.
• Tell your provider and surgeon if you have been drinking a lot of alcohol, more than 1 or 2 drinks per day.
• If you smoke, you need to stop. Ask your providers for help. Smoking will slow down wound and bone healing. Your recovery may not be as good if you keep smoking.
• Always let your surgeon know about any cold, flu, fever, herpes breakout, or other illness you have before your surgery.
• You may want to visit a physical therapist to learn some exercises to do before surgery.
• Practice using a cane, walker, crutches, or a wheelchair correctly.

On the day of your surgery:

• You will most often be asked not to drink or eat anything for 6 to 12 hours before the procedure.
• Take the medicines you have been told to take with a small sip of water.
• You will be told when to arrive at the hospital.

After the Procedure

You may go home the same day or you may stay in the hospital for 1 to 2 days. During that time, you will recover from your anesthesia and from the surgery itself. You will be asked to start moving and walking as soon as the day of surgery.

Full recovery will take 4 months to a year.

Some people need a short stay in a rehabilitation center after they leave the hospital and before they go home. At a rehabilitation center, you will learn how to safely do your daily activities on your own.

Outlook (Prognosis)

The results of a total knee replacement are often excellent. The operation relieves pain for most people. Most people do not need help walking after they fully recover.

Over 90 percent of artificial knee joints last over 15 years. Some last as long as 25 years before they loosen and need to be replaced again. Total knee replacements can be replaced again if they get loose or wear out. However, in most cases the results are not as good as the first time. It is important not to have the surgery too early so you will need another surgery at a young age or have it too late when you will not benefit the most. After surgery, you should have periodic checkups with your surgeon to make sure the parts of your artificial joint are in good position and condition.

Alternative Names

Total knee replacement; Knee arthroplasty; Knee replacement - total; Tricompartmental knee replacement; Subvastus knee replacement; Knee replacement - minimally invasive; Knee arthroplasty - minimally invasive; TKA - knee replacement; Osteoarthritis - replacement; OA - knee replacement

American Academy of Orthopedic Surgeons (AAOS) website. Treatment: total knee replacement. orthoinfo.aaos.org/en/treatment/total-knee-replacement. Updated February . Accessed September 26, .

Ellen MI, Forbush DR, Groomes TE. Total knee arthroplasty. In: Frontera WR, Silver JK, Rizzo TD Jr, eds. Essentials of Physical Medicine and Rehabilitation. 4th ed. Philadelphia, PA: Elsevier; :chap 80.

Mihalko WM. Arthroplasty of the knee. In: Azar FM, Beaty JH, eds. Campbell's Operative Orthopaedics.14th ed. Philadelphia, PA: Elsevier; :chap 7.

Review Date 8/27/

Updated by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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