Total knee replacement

What is a Total Knee Replacement?

The knee joint is made up of the femur (thigh bone) sitting on the tibia (shin bone) with the patella (knee cap) running along a groove in the front of the femur. Arthritis can affect any or all of these parts of the joint. In arthritis, the joint surface cartilage which covers the ends of the bones, is damaged or worn out. When the worn out surfaces rub against each other, they cause pain. In a total knee replacement, the worn out cartilage surfaces are replaced with metal surfaces which are impacted or cemented into the bone; a hard plastic liner sits between the metal surfaces so that they move smoothly.

Who should have a Total Knee Replacement?

If you have arthritis in your knee, the first step is to try simple treatments such as taking painkillers and anti-inflammatories, gentle knee exercises and maybe walking with a stick. Used in combination, these treatments can improve your pain and level of function significantly and you may not need anything else at this stage. If you have tried all of this and you are still getting significant pain and stiffness that is preventing you from doing the things you want to do or you are not able to sleep because of the pain, a total knee replacement may be the best solution for you.

How is a Total Knee Replacement performed?

A total knee replacement is performed under an anaesthetic (either a general or spinal anaesthetic). An incision is made in the front of the knee and the knee joint is opened up. The ends of the femur and tibia are reshaped and the metal replacements are inserted onto the bones. A plastic liner is then locked onto the metal component of the tibia. If the patella is also very worn out, the undersurface of the patella is smoothed off and a plastic button is cemented in to replace the removed bone.

Research has shown that the results of a total knee replacement depend on the position that the prostheses are placed in. The surgeons at Melbourne Hip and Knee use the most current techniques to achieve the best position for the prostheses in your knee.

The operation usually takes 1.5 - 2 hours.

What is the recovery like after a Total Knee Replacement?

After the operation, you are encouraged to get up and walk as soon as possible. You are allowed to put your full weight on the operated leg but will usually have crutches or a frame for support until you are walking confidently and comfortably. You are encouraged to begin physiotherapy exercises straight away to bend ad straighten the knee and to regain muscle strength. Normally, you would remain in hospital for 3 - 5 days. If you are doing very well at that stage, you can be discharged directly home after that. Otherwise, you will be transferred to a rehabilitation hospital for 1 - 2 weeks where physiotherapists will work more closely with you.

You should take regular pain killers and ice the knee regularly for the first few weeks to make the knee feel comfortable and also to allow you to do your physiotherapy exercises. You should wear compression stockings and take daily blood thinners for 1 month after a total knee replacement to decrease the risk of developing blood clots in the calf, which can break off and go to the lungs. You will need 3 - 4 weeks off work and possibly longer if you have a physically demanding job.

It takes several weeks for the pain to settle down and it can be several months before it really feels normal. The most important thing you can do to is work hard with your physiotherapy exercises. This will help you recover faster and give you the best results long term.

After a knee replacement you can get back to normal life. Most activities are safe with a knee replacement: walking, hiking, cycling, swimming, golf, bowls, dancing, even social tennis, horse riding, careful skiing and many others.

How long does a knee replacement last?

Modern total knee replacements usually last for a long time. In the first 10 years, only about 1 in 20 knee replacements need to be redone. The majority of knee replacements will last at least 20 years. In patients over 55 years old, more likely than not, a knee replacement will last the rest of your life. Younger patients tend to wear out knee replacements quicker, but even in patients under 55 years, only 12% of knee replacements need to be redone within 10 years.

What risks are associated with having a Total Knee Replacement?

There are risks associated with the anaesthetic, including the possibility of heart attacks, strokes and breathing difficulties. The chance of these occurring is generally very low and you will be assessed before the operation to see if there is anything that needs to be done to decrease this risk further.

There is a risk of the knee replacement getting infected. This occurs in less than 1 in 100 operations. If the knee replacement gets infected, you may need further operations to wash it out. If the infection is severe, the whole knee replacement may need to be removed and then replaced again once the infection is cured..

There is a small risk of injury to the nerves and blood vessels around the knee. The chance of any major injury is extremely low. You will, however, always develop a patch of numbness on the outer side of the knee which will be permanent to a degree. This is because one of the nerves that provides feeling to that part of the knee always gets cut when the skin is incised.

If you lose a lot of blood from the operation, you may require a blood transfusion.

As mentioned above, there is a risk of developing clots in the legs which can then go to the lungs. You will be given blood thinning medication to reduce this risk.

Over time, there is a chance that the knee replacement will wear out. If this happens, you may need to have a redo, or revision, operation. Generally, most knee replacements last more than 20 years.

If you have any further questions, please ask you surgeon.