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

The operation is done while you are asleep and without pain (general anesthesia). The orthopedic surgeon makes a cut over the affected knee. The knee cap (patella) is moved out of the way, and the ends of the thigh bone (femur) and shin bone (tibia) are cut to fit the prosthesis. The undersurface of the knee cap is cut to allow the surgeon to place an artificial piece.

The two parts of the prosthesis are placed onto the ends of the femur, the tibia, and the undersurface of the 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, surgeons are now using newer surfaces, including metal on metal, ceramic on ceramic, or ceramic on plastic.

In some cases, a mini-incision may be used to avoid cutting the tendon on the front of the knee. This may allow for faster, less painful recovery, but it has risks because of the difficulty of the surgery and the lack of a clear view for the surgeon.

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 help.

Knee joint replacement may be recommended for:

• Knee pain that hasn't responded to other therapy (including medication, injections, and physical therapy for 6 months or more)
• Knee pain that limits or prevents activities
• 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

• Current knee infection
• Poor skin cover around the knee
• Paralysis of the muscles in the front of the thigh (quadriceps)
• Severe peripheral vascular disease or neuropathy that affect the knee
• Severe mental dysfunction
• Terminal disease (for example, cancer that has spread)
• Morbid obesity (over 300 pounds)

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 requiring removal of the joint
• Loosening of the prosthesis
• Displacement of the prosthesis

People who have a prosthetic device (such as an artificial joint) need to carefully protect against infection. You should carry a medical identification card indicating that you have a prosthetic device. Also, always tell your health care provider about your prosthetic knee joint. You should take antibiotics before any dental work or any invasive procedure.

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

After surgery, you will have a large dressing on the knee area. A small drainage tube will be placed during surgery to help drain excess fluids from the joint area.

You will also have an IV in place to provide fluids until you are able to drink. Special stockings are placed on your legs to reduce your risk of getting blood clots, which are more common after leg surgery.

Your doctor will prescribe pain medicines and, possibly, antibiotics to prevent infection.

You will stay in the hospital for 3-5 days, but the total recovery period varies from 2-3 months to a year.

You will be encouraged to start moving and walking as early as the first day after surgery. You will be helped out of bed to a chair on the first day after surgery. When in bed, bend and straighten your ankles often to prevent blood clots.

Some surgeons recommend using a continuous passive motion (CPM) machine that will bend the knee for you while you're in bed. Over time, the rate and amount of bending will increase. Always keep your leg in the CPM device when in bed. This device helps speed recovery, and reduces pain, bleeding, and infection.

Some patients need a short stay in a rehabilitation hospital to become safely independent in their daily activities. You might need to use crutches or a walker for a few weeks or even months after surgery.

The physical therapy started in the hospital will continue after you've gone home until your strength and motion return. Avoid contact sports, but you should be able to do low impact activities, such as swimming and golf, after you fully recover from surgery.