What is a total knee replacement?

 

A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material. The knee is a hinge joint which provides motion at the point where the thigh meets the lower leg. The thighbone (or femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell. The end of the lower leg bone (tibia) 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 artificial components of a total knee replacement are referred to as the prosthesis.

The posterior cruciate ligament is a tissue that normally stabilizes each side of the knee joint so that the lower leg cannot slide backward in relation to the thighbone. In total knee replacement surgery, this ligament is either retained, sacrificed, or substituted by a polyethylene post. Each of these various designs of total knee replacement has its own particular benefits and risks.

Picture of a total knee replacement

Total knee replacement facts

  • Patients with severe destruction of the knee joint associated with progressive pain and impaired function maybe candidates for total knee replacement.

  • Osteoarthritis is the most common reason for knee replacement operation in the U.S.

  • Risks of total knee replacement surgery have been identified.

  • Physical therapy is an essential part of rehabilitation after total knee replacement.

  • Patients with artificial joints are recommended to take antibiotics before, during, and after any elective invasive procedures (including dental work).

 

What is involved with the preoperative evaluation for total knee replacement?

Before surgery, the joints adjacent to the diseased knee (hip and ankle) are carefully evaluated. This is important to ensure optimal outcome and recovery from the surgery. Replacing a knee joint that is adjacent to a severely damaged joint may not yield significant improvement in function as the nearby joint may become more painful if it is abnormal. Furthermore, all medications that the patient is taking are reviewed. Blood-thinning medications such as warfarin(Coumadin) and anti-inflammatory medications such as aspirin may have to be adjusted or discontinued prior to surgery.

Routine blood tests of liver and kidney function and urine tests are evaluated for signs of anemia, infection, or abnormal metabolism. Chest X-ray and EKG are performed to exclude significant heart and lung disease that may preclude surgery or anesthesia. Finally, a knee replacement surgery is less likely to have good long-term outcome if the patient’s weight is greater than 200 pounds. Excess body weight simply puts the replaced knee at an increased risk of loosening and/or dislocation and makes recovery more difficult.