Knee replacement surgery

WEB EXCLUSIVE / NOVEMBER 2005
POSTGRADUATE MEDICINE
Update of a handout originally published in December 1999

Download this Patient Note in PDF format

Damaged knees make everyday activities, such as walking or climbing stairs, difficult and painful. Medications, walkers or canes, and changes in activity level can help. But if they stop working, knee replacement surgery may be an option. The effectiveness of knee replacement surgery, also called arthroplasty (AR-throw-plass-tee), has greatly improved since it was first performed in 1968. Today, 365,000 people in the United States have total knee replacement surgery each year, helping them remain active and pain-free for many years.

How does the knee work?
The largest joint in the body, the knee can bend, slide, and glide through an amazing range of motion. It absorbs up to seven times your body's weight as you go about your normal activities. Obviously, many bones, muscles, tendons, ligaments, and other types of tissue must work together to keep the knee functioning.

When you bend your knee, the end of your thighbone (femur) moves against the top of your shinbone (tibia) like a hinge. A cushion of tough, elastic tissue called cartilage keeps the bones from rubbing directly together. Fibrous ligaments connect the thigh and shin bones, and muscles and tendons stabilize the joint and allow it to move. The kneecap (patella) protects the joint and anchors important tendons.

Why would a knee need to be replaced?
Aging, injury, and disease all cause wear and tear on the knees. The most common reason for knee replacement is osteoarthritis, a gradual breakdown of the cartilage between the femur and tibia. Without the cushion, the bones begin to rub directly together, which causes pain.

Rheumatoid arthritis, an inflammation of the tissue around joints, is another cause of knee pain. Knee injuries sometimes lead to a disorder called posttraumatic arthritis.

Although most people who have this surgery are between 60 and 80 years old, some have been as young as 16 or older than 90. More than 90% of knee replacements result in dramatically reduced knee pain and increased mobility of the knee joint.

How is knee replacement surgery performed?
There are several types of surgery: total knee replacement, partial (unicompartmental) replacement, and replacement of both knees (bilateral). The type of surgery depends on your age, activity level, degree of arthritis, and how much the cartilage and joint are damaged.

Total knee replacement surgery, which takes about 2 hours, consists of removing damaged cartilage and bone and replacing it with an artificial joint (prosthesis) made of metal and plastic. In partial knee replacement, implants take the place of a damaged part or parts of the knee. Recovery is faster than in total knee replacement, but long-term results may not be as good. The best candidate for this type of surgery is younger than 60 years or older than 75 years and inactive but not obese.

Bilateral replacement may be done if severe arthritis is present in both knees. This is a good option for some people because it consists of only one operation, but recovery usually is longer.

How long is recovery from knee replacement surgery?
Most people who have total knee replacement surgery spend 2 to 4 days in the hospital, while people who have bilateral replacement stay for 4 to 6 days, followed by a week in a rehabilitation facility. People who have partial knee replacement typically stay in the hospital overnight. Physical therapy will be given in the hospital to help you get used to your new knee or knees. Your doctor will discuss the possibility of blood clots in the leg, an uncommon complication of surgery. It is important to call your doctor if you notice increasing pain, redness, or swelling.

At home, you'll continue doing exercises you learned in the hospital and will use crutches or a walker. You may also need other adaptive devices, such as safety bars in your shower or bath. Plan to live on one floor of your home during this time, because stairs will be difficult at first.

Eventually, you can use a cane. About 6 weeks after surgery, most people can walk without a cane. Your doctor will help you determine when it's safe to return to work and normal activities. Low-impact exercise, such as swimming or biking over a level surface, is encouraged to help build and maintain muscle strength. High-impact activities that jar the knees, however, should be avoided.

Most replacement joints last for many years, but sometimes, especially in young people who had the surgery, the joints may need repair or replacement if they become worn. Regular checkups with your doctor are important to make sure the joint stays aligned and working correctly.

Although knee replacement surgery is not appropriate for everyone, it has helped many people resume an active life.

This information is not a substitute for medical treatment.

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