Definition of Knee joint replacement:

Knee joint replacement is surgery to replace a knee joint with an artificial joint. The artificial joint is called a prosthesis.

See also: Unicompartmental knee arthroplasty

Description:

Knee joint replacement surgery involves removing damaged cartilage and bone in the knee joint. Man-made (artificial) pieces, called prostheses, are then placed in the knee.

You will not feel any pain during the surgery because you will receive anesthesia. You will have one of these two types of anesthesia:

• General anesthesia. This means you will be unconscious and unable to feel pain.
• Regional (spinal or epidural) anesthesia. Medicine is put into your back to make you numb below your waist. You will also get medicine to make you sleepy.

After you receive anesthesia, your surgeon will make a cut over your knee to open it up. Then your surgeon will:

• Move your kneecap (patella) out of the way, then cut the ends of your thigh bone and shin (lower leg) bone to fit the prosthesis.
• Cut the underside of your kneecap to prepare it for the artificial pieces that will be attached there.
• Fasten the two parts of the prosthesis to your bones. One part will be attached to the end of your thigh bone and the other part will be attached to your shin bone.
• Attach both parts to the underside of your kneecap. A special bone cement is used to attach these parts.
• Repair your muscles and tendons around the new joint and close the surgical cut.

The surgery usually takes around 2 hours.

Usually, artificial knees have both metal and plastic parts. Some surgeons now use different materials, including metal on metal, ceramic on ceramic, or ceramic on plastic.

MINIMALLY INVASIVE KNEE REPLACEMENT

Some surgeons are using a newer surgery technique called "minimally invasive" knee joint replacement. This type of surgery uses a smaller surgical cut.

The surgeon will use special instruments to work through the small cuts. In minimally invasive surgery, your surgeon will:

• Cut and remove bone and cartilage
• Move some muscles and other tissues, but less than in open (traditional) surgery. Fewer muscles around the knee may need to be cut or detached.
• Use the same implants as in open surgery, or use newer implants

Why the Procedure Is Performed:

The most common reason to have a knee joint replaced is to relieve severe arthritis pain. Your doctor may recommend knee joint replacement when:

• You're having symptoms of knee arthritis, such as:
  • You can't sleep through the night because of knee pain
  • Your knee pain limits or keeps you from being able to do your normal activities, such as bathing, preparing meals, and household chores
  • You can't walk and take care of yourself
• Your knee pain has not improved with other treatment
• You understand what surgery and recovery will be like

Knee joint replacement is usually done in people ages 60 and older. Younger people who have a knee joint replaced may put extra stress on the artificial knee and cause it to wear out early.

Some medical problems may lead your doctor to recommend that you not have the surgery. Some of these problems are:

• Knee infection
• Morbid obesity (weighing over 300 pounds)
• Poor blood flow in the leg
• Unhealthy skin around your knee
• Very weak quadriceps, the muscles in the front of your thigh. Weak quadriceps could make it very hard for you to walk and use your knee.

After the Procedure:

You will stay in the hospital for 3 to 5 days, but full recovery will take from 2 to 3 months to a year.

After surgery:

• You will have a large dressing (bandage) over your knee. A small drainage tube will be placed during surgery to help drain fluids that build up in your knee joint after surgery. It will be removed when you no longer need it.
• You will have an IV (a catheter or tube that is inserted into a vein, usually in your arm).
• You may have a Foley catheter inserted into your bladder to drain urine. Usually it is removed 2 or 3 days after surgery.
• You will wear special compression stockings on your legs. These stockings improve blood flow and reduce your risk of getting blood clots.
• Most people will also receive blood-thinning medicine to reduce the risk of blood clots.
• You may be taught how to use a device called a spirometer and do deep breathing and coughing exercises. Doing these exercises will help prevent pneumonia.
• Your doctor will prescribe pain medicines to control your pain. Your doctor may also prescribe antibiotics to prevent infection.

You will be encouraged to start moving and walking as soon as the first day after surgery.

• You will be helped out of bed to a chair on the first day after surgery. When you are in bed, bend and straighten your ankles often to prevent blood clots.
• You will be encouraged to do as much you can for yourself by the second day. This includes going to the bathroom or taking walks in the hallways, always with someone helping you.
• Some surgeons recommend using a continuous passive motion machine (CPM) while you are in bed. The CPM bends your knee for you. Over time, the rate and amount of bending will increase. If you are using this machine, always keep your leg in the CPM when you are in bed. It will help speed your recovery and reduce pain, bleeding, and risk of infection.

Some people need a short stay in a rehabilitation center after they leave the hospital and before they go home. At a rehab center, you will learn how to safely do your daily activities on your own.

Outlook (Prognosis):

The results of a total knee replacement are often excellent. The operation relieves pain for most people, and most people do not need help walking after they fully recover. Most artificial knee joints last 10 to 15 years. Some last as long as 20 years before they loosen and need to be replaced again.

Risks:

Risks for any surgery are:

• Breathing problems
• Infection, including in the lungs, urinary tract, and chest
• Bleeding
• Heart attack or stroke during surgery

The risks of this surgery are:

• Dislocation of the artificial joint
• Infection that requires removing the joint
• Loosening of the artificial joint over time
• Pneumonia
• Allergic reaction to the artificial joint
• Injury to nerves or blood vessels
• Blood clots that may form in your leg (deep vein thrombosis) or your lungs (pulmonary embolism)

Before the Procedure:

Always tell your doctor or nurse what drugs you are taking, even drugs, supplements, or herbs you bought without a prescription.

During the 2 weeks before your surgery:

• Prepare your home.
• Two weeks before surgery you may be asked to stop taking drugs that make it harder for your blood to clot. These include aspirin, ibuprofen (Advil, Motrin), naproxen (Naprosyn, Aleve), and other drugs.
• Ask your doctor which drugs you should still take on the day of your surgery.
• If you have diabetes, heart disease, or other medical conditions, your surgeon will ask you to see the doctor who treats you for these conditions.
• Tell your doctor if you have been drinking a lot of alcohol, more than 1 or 2 drinks a day.
• If you smoke, you need to stop. Ask your doctor or nurse for help. Smoking will slow down wound and bone healing. Your recovery overall may not be as good if you keep smoking.
• Always let your doctor know about any cold, flu, fever, herpes breakout, or other illness you may have before your surgery.
• You may want to visit a physical therapist to learn some exercises to do before surgery.
• Practice using a cane, walker, crutches, or a wheelchair, especially the correct ways to:
  • Get in and out of the shower
  • Go up and down stairs
  • Sit down to use the toilet and stand up after using the toilet
  • Use the shower chair

On the day of your surgery:

• You will usually be asked not to drink or eat anything for 6 to 12 hours before the procedure.
• Take the drugs your doctor told you to take with a small sip of water.
• Your doctor or nurse will tell you when to arrive at the hospital.