What is a knee joint?

In total knee replacement or total knee arthroplasty (TKA), the end of the femur bone and end of the tibia are removed and replaced.
In total knee replacement or total knee arthroplasty (TKA), the end of the femur bone and end of the tibia are removed and replaced.

The knee is the largest joint in the body that consists of the following:

  • Femur (lower end of the thighbone)
  • Tibia (the upper end of the shinbone) 
  • Patella (the kneecap)

The ends of these three bones are covered with a smooth substance called the articular cartilage that protects the bones and enables joint movement. All surfaces of the knee are covered by a thin lining called the synovial membrane. 

This membrane releases a fluid that lubricates the cartilage, reducing friction to nearly zero in a healthy knee. Normally, all these components work in harmony. However, a disease or an injury can disrupt this harmony, resulting in pain, muscle weakness, and reduced function.

What is total knee arthroplasty?

If an individual’s knee is severely damaged by joint swelling or an injury, it may be hard for them to perform simple activities such as walking or climbing stairs. They may even begin to feel pain when they are sitting or lying down.

If nonsurgical treatments, such as medications and using walking supports, are no longer helpful, the patient may consider a surgical procedure called a total knee replacement surgery or total knee arthroplasty (TKA).

Joint replacement surgery is a safe and effective procedure to relieve pain, correct leg deformity, and help the individual resume normal activities. In this procedure, the diseased or injured knee joint is replaced with artificial material.

When does an individual require total knee joint replacement?

Most patients who undergo total knee replacement are between 50 and 80 years old. The total knee replacement surgery is considered for patients whose knee joints have been damaged by below conditions:

  • Osteoarthritis: It is a degenerative joint disease. Patients with this condition are unable to do normal activities due to severe pain. The knee may swell or "give way" because the joint is not stable. It is the most common cause of total knee arthroplasty (TKA).
  • Rheumatoid arthritis: This is a disease in which the synovial membrane that surrounds the joint becomes swollen and thickened. This severe swelling can damage the cartilage and eventually cause pain and stiffness. It is the most common form of a group of disorders termed "inflammatory arthritis."
  • Severe injury to the knee.
  • Knee joint deformity by birth.

What is replaced in total knee arthroplasty?

The artificial components of a total knee replacement are referred to as a prosthesis.

  • During total knee replacement, the end of the femur bone is removed and replaced with a metal shell. The end of the tibia (lower leg bone) is also removed and replaced with a channeled plastic piece with a metal stem.
  • Depending on the condition of the kneecap portion of the knee joint, a plastic "button" may also be added under the kneecap surface.
  • The posterior cruciate ligament is a tissue that normally stabilizes each side of the knee joint so that the lower leg cannot slide backward to the thighbone. In the total knee replacement surgery, this ligament is retained, sacrificed, or substituted by a polyethylene post.

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What happens during total knee arthroplasty?

Total knee arthroplasty (TKA) is major surgery and usually performed under general or spinal anesthesia. Usually, the surgery is completed within three hours, depending upon the patient’s condition.

  • The surgeon monitors the patient’s vitals throughout the procedure.
  • The surgeon cleanses the skin over the surgical site with an antiseptic solution.
  • The orthopedic surgeon will make an incision in the knee area.
  • The surgeon may remove the damaged surfaces of the knee joint and resurface the knee joint with the prosthesis. The prosthesis generally comprises three components: the tibial component (to resurface the top of the tibia or shin bone), the femoral (thigh bone) component (to resurface the end of the thighbone), and the patellar component (to resurface the bottom of the kneecap that rubs against the thighbone).
  • The surgeon closes the incision with stitches or surgical staples.
  • The surgeon may place a drain in the incision site to remove the fluid.
  • The surgeon will apply a sterile bandage or dressing.
  • The patient may be on painkillers and antibiotics. They will be monitored in the intensive care unit (ICU) until they wake up from anesthesia. Depending on the patient’s condition, they may be shifted to the hospital room later.

What are the risks of total knee arthroplasty?

Some possible complications of total knee arthroplasty may include the following:

  • Bleeding
  • Infection
  • Blood clots in the legs or lungs
  • Loosening or wearing out of the prosthesis
  • Fracture
  • Continued pain or stiffness
  • Nerves or blood vessels in the area of surgery may be injured, resulting in weakness or numbness. The joint pain may not be relieved by the surgery.

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Medically Reviewed on 7/29/2020
References
"Total Knee Arthroplasty (TKA)"

Medscape Medical Reference
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