Total knee replacement

Alternative names
Knee joint replacement; Knee arthroplasty

Definition
Knee joint replacement is surgery to replace a painful damaged or diseased knee joint with an artificial joint (prosthesis).

Description

The operation is performed under general anesthesia. The orthopedic surgeon makes an incision over the affected knee. The patella (knee cap) is moved out of the way, and the ends of the femur and tibia are cut to fit the prosthesis and to provide better adhesion of the prosthesis. Similarly, the undersurface of the knee cap is cut to allow for placement of an artificial component.

The two parts of the prosthesis are implanted onto the ends of the thigh bone (femur), the shin bone (tibia), and the undersurface of the knee cap (patella) using a special bone cement. Usually, metal is used on the end of the femur, and plastic is used on the tibia and patella, for the new knee surface. However, newer surfaces including metal on metal, ceramic on ceramic, or ceramic on plastic are now being used.

You will return from surgery with a large dressing to the knee area. A small drainage tube will be placed during surgery to help drain excess fluids from the joint area.

Your leg may be placed in a continuous passive motion (CPM) device after surgery. This is a mechanical device that flexes (bends) and extends (straightens) the knee to keep the knee from getting stiff.

Gradually, the rate and amount of flexion will be increased as tolerated. The leg should always be in this device when in bed. The CPM device helps speed recovery, decreases post-operative pain, bleeding and infection.

You will experience moderate pain after surgery. However, you may receive injections of narcotic medications, patient-controlled analgesia (PCA) or epidural analgesics (spinal) to control your pain for the first 3 days after surgery.

The pain should gradually decrease, and by the third day after surgery, oral medications may be sufficient to control your pain. Try to schedule your pain medications about one half hour before walking or position changes.

You will also return from surgery with several IV lines in place to provide fluid and nutrition. The IV will remain in place until you are taking adequate amounts of fluids by mouth.

Antibiotics may be given to reduce the risk of developing an infection, necessitating removal of the artificial joint.

You will also return from surgery wearing anti-embolism stockings or inflatable pneumatic compression stockings. These devices are used to reduce your risk of developing Blood clots, which are more common after lower extremity surgery.

Additionally, you will be encouraged to start moving and walking as early as the first day after surgery. You will be assisted out of bed to a chair on the first day after surgery. When in bed, bend and straighten your ankles frequently to prevent development of Blood clots.

You may be instructed on how to use an incentive spirometry device (a plastic device to encourage deep breathing), and cough and deep breathing exercises to gradually increase the depth of your respirations in order to prevent lung collapse and Pneumonia.

A foley catheter may be inserted during surgery to monitor the function of your kidneys and hydration level. This will be removed on the second or third day after surgery. You will be encouraged to try to walk to the bathroom with assistance.

Indications
Knee joint replacement may be recommended for:

     
  • knee pain that has failed to respond to conservative therapy (including medication, injections, and physical therapy for 6 months or more)  
  • knee pain that limits or prevents activities of importance to the patient  
  • arthritis of the knee  
  • decreased knee function caused by arthritis  
  • inability to sleep through the night because of knee pain  
  • some tumors involving the knee

Knee joint replacement is usually not recommended for:

     
  • current knee infection  
  • poor skin coverage around the knee  
  • paralysis of the quadriceps muscles  
  • severe peripheral vascular disease or neuropathy affecting the knee  
  • severe limiting mental dysfunction  
  • terminal disease (metastatic disease)  
  • morbid Obesity (over 300 lb.)

Risks
The risks of this surgery include:

     
  • Blood clots in the legs (deep vein thrombosis or DVT)  
  • DVT that breaks loose and goes to the lungs (embolus)  
  • Pneumonia  
  • infection necessitating removal of the joint  
  • loosening of the prosthesis  
  • dislocation of the prosthesis

People who have a prosthetic device (such as an artificial joint) need to take special precautions against infection. You should carry a medical identification card indicating that you have a prosthetic device. Also, always inform your health care provider of your prosthetic knee joint. You should receive prophylactic antibiotics prior to dental work or any invasive procedure.

Expectations after surgery

The results of a total knee replacement are often excellent. The operation relieves pain in over 90% of patients, and most need no assistance walking after recovery. Most prostheses last 10 to 15 years, some as long as 20 years, before loosening and requiring revision surgery.

Convalescence

The hospital stay generally lasts 4-5 days, but the total recovery period varies from 2-3 months to a year. Walking and range-of-motion exercises will be started immediately after surgery. Some surgeons recommend using a machine that will bend the knee for the patient in bed.

Some patients require a short stay in a rehabilitation hospital to become safely independent in their activities of daily living. It may be necessary to use crutches or a walker for a few weeks or even months after surgery.

The physical therapy initiated in the hospital will continue after discharge until your strength and motion return. Contact sports should generally be avoided, but low impact activities, such as swimming and golf, are usually possible after full recovery from surgery.

Johns Hopkins patient information

Last revised: December 2, 2012
by Arthur A. Poghosian, M.D.

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