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 thigh bone (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 plastic piece on a metal base. Depending on the condition of the kneecap portion of the knee joint, a plastic "button" may also be added under the kneecap surface.

Total knee replacement surgery is considered for patients whose knee joints have been damaged by progressive arthritis trauma, or other rare destructive diseases of the joint. The most common reason for knee replacement in the India is severe osteoarthritis of theknees. Regardless of the cause of the damage to the joint, the resulting progressively increasing pain and stiffness, and decreasing daily function lead the patient to consider total knee replacement. Decisions regarding
whether or when to undergo knee replacement surgery are not easy. Patients should understand the risks as well as the benefits before making these decisions.

What are the risks of undergoing a total knee replacement?

Risks of total knee replacement include blood clots in the legs that can travel to the lungs (pulmonary embolism). Pulmonary embolism can cause shortness of breath, chest pain, and even shock. Other risks include urinary tract infection, nausea and vomiting (usually related to pain medication), chronic knee pain and stiffness, bleeding into the knee joint, nerve damage, blood vessel injury, and infection of the knee which can require re-operation. Furthermore, the risks of anesthesia include potential heart, lung, kidney, and liver damage.

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

Before surgery, joints adjacent to the diseased knee are carefully evaluated. This is important to ensure optimal outcome from the surgery. Replacing a knee joint which is adjacent to a severely damaged joint may not yield significant improvement in function. Furthermore, all medications which the patient is taking are reviewed. Blood thinning medications such as 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 ECG are performed to exclude significant heart and lung disease which may preclude surgery or anesthesia. Finally, it 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. A similar risk is encountered in younger patients who may tend to be more active, thereby adding trauma to the replaced joint.

What happens in the postoperative period?

A total knee replacement generally requires between one and one- half to three hours of operative time. After surgery, patients are taken to a recovery room, where vital organs are frequently monitored. When stabilized, patients are returned to their hospital room. Passage of urine can be difficult in the immediate postoperative period, and this condition can be aggravated by pain medications. A catheter inserted into the urethra (a Foley catheter) allows free passage of urine until the patient becomes more mobile.

Physical therapy is an extremely important part of rehabilitation and requires full participation by the patient for optimal outcome. Patients can begin physical therapy forty-eight hours after surgery. Some degree of pain, discomfort, and stiffness can be expected during the early days of physical therapy. Knee immobilizers are used in order to stabilize the knee while undergoing physical therapy, walking, and sleeping. They may be removed under the guidance of the therapist for various portions of physical therapy.