Total Knee Replacement

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Total Knee Replacement

The largest joints in the human body are the knees and having them healthy and functional is vital to performing many everyday activities.  Difficultly doing simple activities like walking or climbing stairs and feeling pain while sitting or lying down, may be symptoms of damage due to arthritis or injury.  When nonsurgical treatments such as supports and medications fail to help, then you may be a candidate for a total knee replacement.  Joint replacement surgery is a safe and effective procedure that is used to relieve pain, corrects deformities and help patients resume normal daily activities.

Since the first knee replacement surgery done in 1968, there have been a great many improvements in both the surgical techniques and materials which have increased the effectiveness making this one of the most successful procedures in orthopedic medicine.  It is estimated that in the United States alone more than 600,000 knee replacements are performed each year.

Anatomy

The knee joint is formed by the distal end of the femur (thighbone), the proximal end of the tibia (shinbone) and the patella (kneecap).  The end of each of these three bones is covered with cartilage which allows them to move smoothly at the point which they converge.  Furthermore, there are c-shaped wedges called menisci that serve as shock absorbers between the thighbone and tibia.  Stability is provided by several large ligaments (e.g. ACL, MCL, LCL and MCL) while knee strength come principally from the thigh muscle.  The remaining knee surfaces are covered by a synovial membrane which is a thin membrane that releases joint fluid to lubricate the cartilage.  In normal healthy knees, this design has little friction at the bone meeting points, but when there is disease or injury this smooth operation is disrupted causing abnormal wear that leads to pain and reduced function.

Most Common Causes of Knee Pain and Disability

Arthritis is the most common cause of disability and pain in the knee.  While there are many types of arthritis the three most related to knee pain are Osteoarthritis, Rheumatoid Arthritis and Post-Traumatic Arthritis.

Osteoarthritis: Typically seen in patients who are 50 and older (though it can occur in younger patients), osteoarthritis is due to age-related wear of the cartilage that cushions the knee.  As this cartilage ages and succumbs to normal use, it softens and begins to wear away causing the bones to rub against each other creating friction that then leads to knee pain and stiffness.

Rheumatoid Arthritis:  When the thin (synovial) membrane that surrounds the knee and that releases joint fluid to lubricate the cartilage becomes chronically inflamed, it damages the knee cartilage.  This damage causes abnormal wear and loss of the cartilage which in turn leads to stiffness and pain.  Since this is an “inflammatory disorder” it is often treated first with anti-inflammatory medications.

Post-Traumatic Arthritis: Serious damage to a knee such as fractures of the bones that make up the knee or ligament tears can cause damage to the cartilage that covers the bone ends (articular cartilage) leading to pain and limited function over time.

General Description of a Knee Replacement Surgery (Arthroplasty)

While an Arthroplasty is more commonly known as a knee replacement in actuality it is more of a knee ‘resurfacing’ where the damaged cartilage on the end of the bones and the shock absorbing menisci are replaced giving the knee a smooth frictionless movement.  The procedure consists of four basic steps:

  • Bone Preparation: The ends of the two bones (the femur and tibia) that meet in the knee joint have the damaged cartilage and some underlying bone removed.
  • Implant placement: Precision engineered metal components are cemented or affixed on the bone surface where the cartilage was removed recreating the natural surface of the joint.
  • Patella (knee cap) resurfacing: Depending on the case, some surgeons will resurface the underside of the kneecap with a plastic button.
  • Meniscus Replacement (Spacer Insert): A specially designed and manufactured plastic spacer that is used to replace the meniscus is inserted between the metal components attached to the ends of the bones. This creates the smooth sliding surface upon which the metal ends move.

Are you a candidate for a Knee Replacement Surgery?

While most patients who have a total knee replacement surgery are between the ages of 50 and 80, there are no absolute age or weight restrictions.  Total knee replacement surgery has been successfully done on patients of all ages from teenagers to the elderly.  The criteria for this surgery are based on pain and disability of the patient and not their age.

There are many reasons an orthopedic surgeon would recommend a patient for a total knee replacement. Those people who would most benefit often present with:

  • Knee stiffness and pain so severe that it limits them from doing everyday activities such as: walking, going up and down stairs and getting in and out of chairs.
  • Knee pain that is severe even when resting
  • Chronic inflammation and swelling that does not respond to medications and rest
  • Deformity of the knee
  • Failure of the knee to respond to other non-surgical treatments such anti-inflammatory medications, injections, physical therapy or other less invasive surgeries.

Total Knee Replacement Surgery

Total Knee Replacement Surgery is a procedure that is performed in a hospital that will require the patient to be admitted.  While the surgery itself takes approximately one to two hours, the patient’s hospital stay will be for several days.

After the surgery and during the recovery in the hospital, it is common for the patient to have some post-surgical pain.  The surgeon will prescribe medication to make the patient feel comfortable, but this pain is important to the recovery process.  Most patients begin physical rehab the day after surgery with walking and knee movements.  The patient’s pain levels are used as a guide to increasing movement and activity and when to rest.

Potential Complications

Complication rates after a total knee replacement surgery is very low with serious complications like infections of the knee joint occurring in fewer than 2% of patients.  Even less frequent are major medical complications such as stroke or heart attacks.  As stated previously, though rare the most common complications of surgery are:

Infection: As with any surgery, the potential of infection is very real and is addressed during the surgery.

Blood clots: It is common in knee replacement surgery for blood clots to form in the leg veins.  These clots can be life-threatening hence why often blood thinning medication is used for a short period prior and after surgery.  Additionally, your doctor will have a prevention program to increase circulation that may include support stocking and leg exercises.

Implant issues: Although implants are meticulously designed and tested and surgical techniques have greatly advanced, on very rare occasions the components can loosen and wear.

Pain: While rare, a small number of patients continue to have post-surgical pain, most patients experience great relief.

Outcomes

Today, more than 90% of total knee replacements are still functioning after 15 years.  That is to say that in most cases and with typical patients, their knee replacement will last a lifetime.  Additionally, most knee replacements result in a dramatic reduction in knee pain as well as substantially increased mobility.

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