What is Total Knee Replacement (TKR) Surgery?

Osteoarthritis is a common form of disability for elderly patients. Knee arthroplasty is performed over 300,000 times per year to help patients relieve pain and restore function in their joints. A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material.

How is Knee Replacement Performed?

The knee is a hinge joint which provides motion at the point where the thigh meets the lower leg. The thigh bone (femur) meets the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur is removed and replaced with a metal shell. The end of the tibia is also removed and replaced with a sculpted plastic piece with a metal stem (as in the diagram below).

The posterior cruciate ligament is a tissue that normally stabilizes each side of the knee joint so that the lower leg cannot slide backwards in relation to the thigh bone. In total knee replacement surgery, this ligament is either retained or sacrificed or substituted by a polyethylene post, each of which has its benefits and risks.

During the procedure, your knee is in a bent position so that all surfaces of the joint are fully exposed. After making an incision between 6 and 12 inches in length, your surgeon moves aside your muscles, kneecap and connective tissues and cuts away the damaged joint surface. He or she takes measurements to ensure a good fit for your new prosthesis and smoothes your bones' rough edges.

The surgeon then inserts the prosthesis. Before closing the incision, he or she bends and rotates your knee, testing and balancing it to ensure that it functions properly.

What is Knee Surgery with the Navigator?

Johnson and Johnson's new computer navigator is a major breakthrough, as it has helped to perfect total knee replacement surgery. The navigator helps surgeons pinpoint the anatomical axis while performing the surgery. This is crucial because the axis differs from person to person. Even if there was a one per cent error in fixing the anatomical axis, the alignment would be incorrect, leading to early wear and tear in the polyethylene liner, similar to a mal-aligned car tyre.

How Will I Feel Post-op?

A total knee replacement generally requires between 1 ½ to 3 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. Post-op pain can be managed with pain medication and ice to reduce swelling.

Passage of urine can be difficult in the immediate post-op 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 (in the short term) and requires full participation by the patient for optimal outcome. Patients can begin physical therapy 48 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.

For several weeks after the procedure, you may need the assistance of crutches or a walker. Mediseekers' carer will look after you during this recovery period, transporting you home, helping with laundry, cooking and bathing (if you require).

What are the Risks and Benefits?

Risks of total knee replacement include blood clots in the legs that can travel to the lungs (pulmonary embolism). This 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 anaesthesia include potential heart, lung, kidney, and liver damage. The benefits include becoming more active again with a major reduction in pain.

Am I a Candidate for Knee Surgery?

Total knee replacement surgery is considered for patients whose knee joints have been damaged by progressive arthritis, trauma or some other destructive disease of the joint. The most common reason for knee replacement in the United States is severe osteoarthritis of the knees.

Regardless of the cause of the damage, the progressively increasing pain, stiffness and decreasing level of activity lead the patient to consider total knee replacement. Decisions regarding whether or not to undergo knee replacement surgery are rarely easy. Patients should understand the risks as well as the benefits before making these decisions.

When Can I Fly After Surgery?

There is no universal agreement as to when it is safe to travel by plane after a knee replacement. Most Orthopaedic surgeons advise their patients not to fly for 4 to 6 weeks following a knee replacement. Some surgeons have pointed to an increased incidence of spontaneous DVT (deep venous thrombosis) on flights. However, the medications provided help thin the blood. Some surgeons suggest wearing below-the-knee graded compression stockings to reduce DVT. Also, doing leg exercises and ankle pumps will help on the flight. Booking an aisle seat (or business class) in advance is recommended for flights.

What Do I Need to Do to Prepare for Knee Surgery?

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. X-rays will be done to evaluate the bones of the knee. Your orthopaedic surgeon may also arrange for you to undergo magnetic resonance imaging (MRI) to provide more information about the soft tissues of your knee. Blood tests may be obtained to determine if you have arthritis.

Furthermore, any medications which 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 anaemia, infection or abnormal metabolism.

Chest X-rays and EKG's are performed to exclude significant heart and lung disease which may preclude surgery or anaesthesia. Finally, it is less likely to have good long-term results if the patient's weight is greater than 200 pounds. Excess body weight simply puts the replaced knee at an increased risk of loosening or dislocation. Similarly, younger patients, who may tend to be more active, can easily place excess stress on the replaced joint.

What Are the Long Term Effects?

More than 95 percent of people who have a total knee replacement experience significant pain relief, improved mobility and a better overall quality of life. Three to six weeks after the procedure, you generally can resume most normal daily activities such as shopping and light housekeeping. Driving is possible in four to six weeks if you can bend your knee far enough to sit in a car and you have enough muscle control to operate the brakes and accelerator properly.

After you've recovered, you can enjoy a variety of low-impact activities, such as walking, swimming, playing golf or biking. But higher impact activities, such as jogging, skiing, tennis, and sports that involve contact or jumping may be out. Talk to your doctor about your limitations.

The studies of modern knee arthroplasty report clinical survivorship of up to 96% of total knee implants at 10 to 15 years. The average survivorship of total knees seems to be approximately 12 years.

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