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Knee Replacement

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If your knee is severely damaged by arthritis or injury, it may be hard for you to perform simple activities such as walking or climbing stairs. You may even begin to feel pain while you’re sitting or lying down. If medications, changing your activity level and using walking supports are no longer helpful, you may want to consider total knee replacement surgery. By resurfacing your knee’s damaged and worn surfaces, total knee replacement surgery can relieve your pain, correct your leg deformity and help you resume your normal activities.

One of the most important orthopedic surgical advances of the twentieth century, knee replacement was first performed in 1968. Improvements in surgical materials and techniques since then have greatly increased its effectiveness. Approximately 300,000 knee replacements are performed each year in the United States.

How the Normal Knee Works
The knee is the largest joint in the body. Nearly normal knee function is needed to perform routine everyday activities. The knee is made up of the lower end of the thigh bone (femur), which rotates on the upper end of the shin bone (tibia), and the knee cap (patella), which slides in a groove on the end of the femur. Large ligaments attach to the femur and tibia to provide stability. The long thigh muscles give the knee strength.

The joint surfaces where these three bones touch are covered with articular cartilage, a smooth substance that cushions the bones and enables them to move easily.

Normally, all of these components work in harmony. But disease or injury can disrupt this harmony, resulting in pain, muscle weakness and less function.

Common Causes of Knee Pain and Loss of Knee Function
The most common cause of chronic knee pain and disability is arthritis. Osteoarthritis, rheumatoid arthritis and traumatic arthritis are the most common forms.

Is Total Knee Replacement for You?
The decision whether to have total knee replacement surgery should be a cooperative one between you, your family, your family physician and your mmpc orthopedic surgeon. Alternatives to traditional total knee replacement surgery that your orthopedic surgeon may discuss with you include a unicompartmental knee replacement or a minimally invasive knee replacement. Reasons that you may benefit from total knee replacement commonly include:

  • Severe knee pain that limits your everyday activities, including walking, going up and down stairs, and getting in and out of chairs. You may find it hard to walk more than a few blocks without significant pain and you may need to use a cane or walker.
  • Moderate or severe knee pain while resting, either day or night
  • Chronic knee inflammation and swelling that doesn’t improve with rest or medications
  • Knee deformity–a bowing in or out of your knee
  • Knee stiffness–inability to bend and straighten your knee
  • Failure to obtain pain relief from non-steroidal anti-inflammatory drugs. These medications, including aspirin and ibuprofen, often are most effective in the early stages of arthritis. Their effectiveness in controlling knee pain varies greatly from person to person. These drugs may become less effective for patients with severe arthritis.
  • Inability to tolerate or complications from pain medications
  • Failure to substantially improve with other treatments such as cortisone injections, physical therapy, or other surgeries

Orthopedic Evaluation
The orthopedic evaluation consists of several components:

  • A medical history
  • A physical examination to assess your knee motion, stability, strength and overall leg alignment
  • X-rays to determine the extent of damage and deformity in your knee
  • Occasionally blood tests, a Magnetic Resonance Image (MRI) or a bone scan may be needed to determine the condition of the bone and soft tissues of your knee.

Your orthopedic surgeon will review the results of your evaluation with you and discuss whether total knee replacement would be the best method to relieve your pain and improve your function. Other treatment options–including medications, injections, physical therapy, or other types of surgery–also will be discussed and considered.

Realistic Expectations About Knee Replacement Surgery
An important factor in deciding whether to have total knee replacement surgery is understanding what the procedure can and can’t do. More than 90 percent of individuals who undergo total knee replacement experience a dramatic reduction of knee pain and a significant improvement in the ability to perform common activities of daily living. But total knee replacement won’t make you a super-athlete or allow you to do more than you could before you developed arthritis.

Following surgery, you will be advised to avoid some types of activity, including jogging and high impact sports, for the rest of your life.

With normal use and activity, every knee replacement develops some wear in its plastic cushion. Excessive activity or weight may accelerate this normal wear and cause the knee replacement to loosen and become painful. With appropriate activity modification, knee replacements can last for many years.

Your Surgery
The procedure itself takes about two hours. Your mmpc orthopedic surgeon will remove the damaged cartilage and bone and then position the new metal and plastic joint surfaces to restore the alignment and function of your knee.

Many different types of designs and materials are currently used in total knee replacement surgery. Nearly all of them consist of three components: the femoral component (made of a highly polished strong metal), the tibial component (made of a durable plastic often held in a metal tray), and the patellar component (also plastic).

Unicompartmental Knee Replacement
Although not as common as total knee replacement, the partial or unicompartmental knee replacement is a viable alternative in limited situations.

The "uni," as it is commonly called, is used to replace a single compartment of the arthritic knee. The knee joint has three compartments: the medial (inner) compartment, the lateral (outer) compartment and the patellofemoral (kneecap) compartment. If the damage is limited to either the medial or lateral compartment, that compartment may be replaced with the uni.

If two or more compartments are damaged, the uni may not be the best option. The uni is also less desirable for a young, active person because it may not withstand the extremes of stress that high levels of activity create. It is best suited for the older, slim person with a relatively sedentary lifestyle. Only between six and eight out of 100 patients with arthritic knees are good candidates for a unicompartmental knee replacement.

Because the uni can be inserted through a relatively small incision (about 3" or 4" long), which does not interrupt the main muscle controlling the knee, rehabilitation is faster, hospitalization is shorter and return to normal activities is more rapid than after a total knee replacement.

Minimally Invasive Knee Replacement
The minimally invasive approach to the total knee replacement is appropriate for non-obese patients who have reasonable motion without significant deformity. Hospitalization may be reduced to one to three days among these patients, and the need for an extended stay for inpatient rehabilitation may be reduced or eliminated in most patients.

Your Stay in the Hospital
You will most likely stay in the hospital for several days. After surgery, you will feel some pain, but medication will be given to you to make you feel as comfortable as possible. Pain management is an important part of your recovery, so talk with your surgeon if postoperative pain becomes a problem. Walking and knee movement are important to your recovery and will begin immediately after your surgery.

To restore movement in your knee and leg, your surgeon may use a knee support that slowly moves your knee while you are in bed. The device, called a continuous passive motion (CPM) machine, decreases leg swelling by elevating your leg and improves your venous circulation by moving the muscles of your leg.

Foot and ankle movement also is encouraged immediately following surgery to increase blood flow in your leg muscles to help prevent leg swelling and blood clots. Most patients begin exercising their knee the day after surgery. A physical therapist will teach you specific exercises to strengthen your leg and restore knee movement to allow walking and other normal daily activities soon after your surgery.

Possible Complications After Surgery
The complication rate following total knee replacement is low. Serious complications, such as a knee joint infection, occur in less than 2 percent of patients. Major medical complications such as heart attack or stroke, occur even less frequently.

Blood clots in the leg veins or pelvis are the most common complications of knee replacement surgery. Your orthopedic surgeon may prescribe one or more measures to prevent blood clots from forming in your leg veins or becoming symptomatic.

How Your New Knee is Different
You may feel some numbness in the skin around your incision. You also may feel some stiffness, particularly with excessive bending activities. Improvement of knee motion is a goal of total knee replacement, but restoration of full motion is uncommon. The motion of your knee replacement after surgery is predicted by the motion of your knee prior to surgery.

Most patients can expect to nearly fully straighten the replaced knee and to bend the knee sufficiently to go up and down stairs and get in and out of a car. Kneeling is usually uncomfortable, but it is not harmful.

Your new knee may activate metal detectors required for security in airports and some buildings. Tell the security agent about your knee replacement if the alarm is activated. You may ask your orthopedic surgeon for a card confirming that you have an artificial knee.

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