Knee joint replacements

Knee joint replacement surgery may be total where both sides of the knee joint are replaced, or uni-compartmental where only one side of the knee joint is replaced. The procedure is performed by separating muscles and ligaments around the knee to expose the knee capsule, and then the inside of the joint.

The ends of the thigh bone (femur) and the shin bone (tibia) are removed and often the underside of the kneecap (patella) is removed. The artificial parts are cemented into place. The new knee joint will consist of a metal shell on the end of the femur, a metal and plastic trough on the tibia and, if needed, a plastic button in the kneecap.

How long will the joint last?

About 85-95% of total knee replacements are successful for more than 10 years. The major long term problem is loosening. Loosening is in part related to your weight and activity, and for that reason replacements may not be considered on the very obese or very young.

A loose, painful prosthesis can usually, but not always, be replaced. The results of the second operation are not as good as the first and the risks of complications are higher.

What happens after surgery?

Once you are back in your room after surgery, the rest of your hospital stay will focus on helping you begin to walk again before going home. You will start on a physical therapy programme to exercise your knee muscles and regain strength and range of motion in your new knee.

During the next few days you will be asked to wiggle your toes and do other easy exercises to improve your circulation.

You will be given a specially designed programme to strengthen your muscles and to start to walk with a walker, then with crutches and then a cane, to help regain confidence and your normal walking motion. This programme will need to be continued when you get home.

The importance of caring for your prosthesis is the result of many years of research. Like any other device, your new knee's life span depends on how you care for it.

Precautions after knee joint replacement

• Follow your surgeon's advice on using crutches or cane to keep weight off your healing knee.
• Keep in mind that your prosthesis is designed for activities of daily living, not sports.
• Before dental work or surgery, let your dentist know you have a prosthesis; antibiotics may be needed to prevent infection.

Call your doctor/surgeon if you have increased knee pain, swelling, incision draining, chest pain, shortness of breath, or any other symptoms you do not understand.

See also: Risks and benefits of joint surgery

Original material provided by Arthritis New Zealand. Edited by everybody, July 2005.