Mayo Clinic Health Library

Knee replacement

Updated: 10-30-2012

Definition

Knee replacement surgery — also known as knee arthroplasty (ARTH-row-plas-tee) — can help relieve pain and restore function in severely diseased knee joints. During knee replacement, a surgeon cuts away damaged bone and cartilage from your thighbone, shinbone and kneecap and replaces it with an artificial joint made of metal alloys, high-grade plastics and polymers.

The first artificial knees were little more than crude hinges. Now, you and your doctor can choose from a wide variety of designs that take into account your age, weight, activity level and overall health. Most knee replacement joints attempt to replicate your knee's natural ability to roll and glide as it bends.

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Why it's done

The most common reason for knee replacement surgery is to repair joint damage caused by osteoarthritis or rheumatoid arthritis. People who need knee replacement surgery usually have problems walking, climbing stairs, and getting in and out of chairs. They may also experience moderate or severe knee pain at rest.

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Risks

As with any surgery, knee replacement surgery carries risks, including:

  • Infection
  • Blood clots in the leg vein or lungs
  • Heart attack
  • Stroke
  • Nerve damage

Signs of infection
Although the risk of infection is low, notify your doctor immediately if you notice:

  • Fever greater than 100 F (37.8 C)
  • Shaking chills
  • Drainage from the surgical site
  • Increasing redness, tenderness, swelling and pain in the knee

An infected knee replacement usually requires surgery to remove the artificial parts and antibiotics to kill the bacteria. After the infection is cleared, another surgery is performed to install a new knee. Your chances of a good or excellent outcome that reduces pain and improves function decline with each additional surgery.

Artificial knees can wear out
Another risk of knee replacement surgery is failure of the artificial joint. Subjected to daily stress, even the strongest metal and plastic parts eventually wear out. You're at a greater risk of joint failure if you put more stress on the joint with high-impact activities or excessive weight.

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How you prepare

An orthopedic surgeon performs knee replacement procedures. Before the procedure, the surgeon takes your medical history and performs a physical examination to assess your knee's range of motion, stability and strength. X-rays can help determine the extent of knee damage.

Knee replacement surgery requires anesthesia to make you comfortable during surgery. Your input and personal preference help the team decide whether to use general anesthesia, which renders you unconscious during the operation, or spinal or epidural anesthesia, during which you are awake but can't feel any pain from your waist down.

Your doctor or anesthesiologist may advise you to stop taking certain medications and dietary supplements before your surgery. You'll likely be instructed not to eat anything after midnight before your surgery.

Plan ahead for your recovery after surgery
For several weeks after the procedure, you may need the assistance of crutches or a walker. Make advance arrangements for transportation home from the hospital and help with everyday tasks such as cooking, bathing and doing laundry. If you live alone, your surgeon's staff can suggest a temporary caretaker.

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

  • Create a total living space on one floor since climbing stairs can be difficult.
  • Install safety bars or a secure handrail in your shower or bath.
  • Secure handrails along your stairways.
  • Obtain 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.
  • Try a stable bench or chair for your shower.
  • Remove all loose carpets and cords.
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What you can expect

During knee replacement surgery
During the procedure, your knee is in a bent position so that all surfaces of the joint are fully exposed. After making an incision about 6 to 10 inches (15 to 25 centimeters) in length, your surgeon moves aside your kneecap and cuts away the damaged joint surfaces.

After the joint surfaces are prepared, the surgeon inserts and attaches the pieces of the artificial joint. Before closing the incision, he or she bends and rotates your knee, testing and balancing it to ensure that it functions properly. Expect knee replacement surgery to last about two hours.

After knee replacement surgery
After surgery, you're wheeled to a recovery room for one to two hours. You're then moved to your hospital room, where you typically stay for a couple of days before going home. You may feel some pain, but medications prescribed by your doctor should help control it.

During the hospital stay, you're encouraged to move your foot and ankle, which increases blood flow to your leg muscles and helps prevent swelling and blood clots. You may need to receive blood thinners and wear support hose or compression boots to further protect against swelling and clotting.

The day after surgery, a physical therapist shows you how to exercise your new knee. During the first few weeks after surgery, you're more likely to experience a good recovery if you follow all of your surgeon's instructions concerning wound care, diet and exercise. Your physical activity program needs to include:

  • A graduated walking program — first indoors, then outdoors — to gradually increase your mobility
  • Slowly resuming other normal household activities, including walking up and down stairs
  • Knee-strengthening exercises you learned from the hospital physical therapist, performed several times a day
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Results

Most people who have a knee replacement experience significant pain relief, improved mobility and a better overall quality of life. Talk with your doctor about what you can expect from knee replacement surgery.

Four to six weeks after knee replacement surgery, you generally can resume most normal daily activities such as shopping and light housekeeping. Driving is also possible at around four weeks if you can bend your knee far enough to sit in a car and you have enough muscle control to properly operate the brakes and accelerator.

After you've recovered, you can enjoy a variety of low-impact activities, such as walking, swimming, golfing or biking. But you should avoid higher impact activities — such as jogging, skiing, tennis, and sports that involve contact or jumping. Talk to your doctor about your limitations.

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