Knee Joint Replacement

Alternate Names
total knee replacement
TKR
total knee arthroplasty
total knee joint replacement



Definition of Knee Joint Replacement

Knee joint replacement is surgery to replace a damaged or diseased knee joint with an artificial joint, or prosthesis. The goal is to improve the mobility and function of the knee joint and reduce pain.

Who is a candidate for the procedure?

Knee joint replacement may be used for long-standing knee pain or arthritis that has not responded to treatment with medication. It may also be used when arthritis causes the knee to function poorly, or for some knee fractures.

The procedure is generally reserved for a person who has knee pain severe enough to stop him or her from working, sleeping well, or walking more than 3 blocks. Most people who have a knee joint replacement are over the age of 55, but it can be performed at any age if it is needed.

How is the procedure performed?

Knee joint replacement is performed under general anesthesia or regional anesthesia. General anesthesia means the person is put to sleep with medications. Regional anesthesia means the person will be awake, but numb below the waist. A drug may be given to make the person drowsy.

The ends of the thighbone (femur), and the shinbone (tibia) are removed. The underside of the kneecap (patella) may also be removed. The new knee consists of a metal shell on the end of the femur and a metal and plastic piece on the tibia. If needed, there is also a plastic button in the kneecap.

The surgery itself takes about 2 hours. In many cases people donate 2 units of their own blood in the weeks before surgery to be used during or shortly after the operation.

What happens right after the procedure?

After the surgery, the person will be taken to the surgery recovery room to be watched closely for a short time. Vital signs, blood pressure, pulse, and breathing will be checked frequently. Close attention will be paid to the circulation and sensation in the legs and feet. The person will receive intravenous fluids to replace those lost during surgery.

There may be a tube near the incision to drain fluid, and a catheter to drain the urine until the person is able to use the bathroom. Pain medication will be available. A continuous passive motion machine (CPM), is often applied to the leg after surgery. This is used to gently bend and straighten the knee. That way, the range of motion is increased, and there is not as much stiffness.

While in the hospital the person will have physical therapy to learn exercises to strengthen the muscles around the knee joint. The person will start bearing weight on the knee, using a walker, the first day after surgery. He or she will also be taught how to use crutches and how to climb stairs at home. Most people are discharged from the hospital 4 to 6 days after the operation.

What happens later at home?

By the time the person is ready to go home, he or she should be able to get around with a walker. People use a walker for 1 to 2 weeks, then use crutches, and then a cane. If all goes well, no walking aids are needed after 3 weeks to 2 months.

Physical therapy may be continued after leaving the hospital. Sometimes people need to go to a rehabilitation center after the hospital. There they can gain the independence they need to be able to get around at home.

Complete recovery from knee joint replacement usually takes from 3 to 6 months. About 90% of artificial knee joints last for 10 years, and 80% last for 20 years, depending on the person's activity level.

What are the potential complications after the procedure?

Like any surgery, knee replacement may be complicated by bleeding, infection, or an allergic reaction to the anesthetic. Other possible complications are urinary tract infections and blood clots in the leg or the lung. To prevent the joint from becoming infected in the future, the person will need to take antibiotics immediately before the start of any dental work.