Knee Replacement

WHAT IS A TOTAL KNEE REPLACeMENT?

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A total knee replacement is an operation in which the surfaces of the damaged knee joint are removed, and replaced with a prosthetic implant. This implant is made up of three main parts; the femoral component, the tibial component, and the plastic (polyethylene) liner. The back of the kneecap may also be resurfaced with a plastic implant called the patella button. Since it was first performed in 1974, knee replacement has become one of the most successful operations invented. Knee replacement surgery is a safe and effective procedure that can relieve your pain, increase motion, and help you get back to enjoying normal, everyday activities.

WHAT CONDITIONS CAN BE TREATED WITH A KNEE REPLACEMENT?

A knee replacement is the surgical solution for a large number of conditions which can affect the knee joint. These include:

  • Osteoarthritis

  • Inflammatory or rheumatoid arthritis

  • Avascular necrosis

  • Post-injury (post-traumatic) arthritis

Follow this link to learn more about knee arthritis. Knee replacement surgery is only indicated when appropriate non-surgical treatment is no longer effective. Mr Gormack will assess your individual circumstances, and can advise whether knee replacement is the right option for you.

HOW IS THE SURGERY performed?

The majority of knee replacement operations are done under spinal anaesthetic. This involves a small injection in your back that makes the lower half of your body completely numb for around about four hours. If you prefer to be asleep for your surgery then you will be given a general anaesthetic. Your leg is cleaned with antiseptic fluid, and sterile surgical drapes are placed. An incision is made over the front of your knee. A computer navigation system is used to position specialised cutting guides, and the worn surfaces of the bones are removed with a precise surgical saw. The new implants are secured into your knee joint before your skin is closed with dissolving stitches. Dressings are put on, including paper stitches (steri-strips) and a waterproof dressing. You will be moved onto a comfortable bed and taken to the recovery area to wake up. A knee replacement operation usually takes around 90 minutes. While you are in the recovery area, an x-ray will be taken of your new knee joint.

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WHAT TYPE OF KNEE IMPLANT WILL BE USED?

There are many different types of knee implant, and the implants come in a range of sizes. All modern knee replacement implants follow similar design principles. Mr Gormack only uses knee replacement implants from one of the largest global implant companies, which has been designing orthopaedic implants for over 40 years. The implant you will receive has excellent results in the New Zealand and international joint registry databases.

Knee implants are made from a proven combination of highly durable materials. The metal parts of the implants which line the end of the thigh bone and shin bone are made from a very strong metal alloy containing titanium and cobalt. The liner, which acts as the new cartilage layer in the middle of the joint, is formed from extremely hard-wearing plastic called highly cross-linked polyethylene. In the majority of people, the implants are secured to the bone with a bone cement called poly-methyl methacrylate (PMMA). Cement-less implants are sometimes used in patients with harder or thicker bone. Before surgery you will have a templating x-ray to ensure the correct size and shape implant is selected for you.

WHAT SHOULD I DO BEFORE SURGERY?

The results of surgery are dependent on both the operation done by your surgeon, but also your health and wellness prior to the operation. Making the following changes to your lifestyle will give you the best possible outcome from your surgery:

  • Reduce or quit smoking

    • Smoking slows wound healing and increases your risks of infection after surgery. Ask your GP for help or call Quitline on 0800 778 778.

  • Reduce alcohol intake

    • Alcohol can have an affect on the medications used during your operation, and can increase the risk of confusion after surgery.

  • Keep active with regular exercise

    • Daily low impact exercise improves your overall fitness and maintains muscle strength. This will help you rehabilitate more quickly after surgery.

    • Cycling, swimming and walking (if tolerated) are all good ways to stay fit.

  • Stay on top of your pain

    • Take regular simple pain medication such as paracetamol or Celebrex. This will allow you to sleep comfortably and maintain regular exercise until your surgery date.

  • Choose mainly healthy foods to eat

    • A balanced diet with lots of fruit, vegetables and lean protein will improve your recovery and healing after surgery. Cut down on fast foods, takeaways and sugary drinks.

  • See your dentist

    • Broken or damaged teeth can be a source of infection in your bloodstream, which can get into your new knee joint. These should be treated at least a week prior to your surgery.

  • Good control of diabetes

    • Poorly-controlled diabetes is one of the biggest risks for infection after your knee replacement. High blood sugars help infection grow.

    • Keeping tight control of your blood sugar levels for weeks or ideally months before surgery is needed to reduce your risk.

    • Your GP can check your long-term blood sugar control with a blood test called HbA1c. Ideally this should be below 55.

  • Treat iron deficiency anaemia

    • If you are anaemic (low in iron) before surgery you have a higher risk of needing a blood transfusion.

    • Eating lean red meat regularly helps to improve iron levels if you are low. Occasionally iron tablets are required. If you are unsure you can be tested by your GP with a simple blood test.

  • Lose some weight if you are overweight

    • Being overweight increases the risk of infection after surgery, and makes rehabilitation harder.

    • Ideally Body Mass Index (BMI) would be under 30, but this is not a realistic goal for many people. Whatever your size, even small amounts of weight loss are helpful and worthwhile.

WHAT IS THE RECOVERY AFTER SURGERY?

After surgery is complete, you will be taken to a ward in another part of the hospital. If you have had a spinal anaesthetic, your legs will stay numb for another 2-3 hours. You can eat and drink normally as soon as you feel ready. Your nurse will monitor your pulse, blood pressure and oxygen levels. They will also provide you with pain relief and anti-nausea medication as required. It is better to keep on top of pain instead of letting it build up. You will have foot pumps on your feet to help keep your circulation moving and prevent blood clots in your legs. Moving your feet regularly yourself also helps to prevent clots. Once you can feel your legs again, you will be encouraged to get out of bed and start walking. A physiotherapist will help you the first time you stand up. Most patients are able to stand and even walk a few steps on the same day as surgery. It is very common to feel a bit faint or dizzy the first time you stand up.

The average stay in hospital after knee replacement surgery is around 2-3 nights. Mr Gormack will check on you each day while you are in hospital. A physiotherapist will see you daily; they will teach you how to walk with a frame or crutches, and give you exercises to do yourself. Once you are confident and safe to walk around and do your daily activities independently, you will be cleared by the physiotherapist to go home. Before you go home you will also be taught knee exercises to do at home as part of your ongoing rehabilitation.

It generally takes around six months to fully recover from knee replacement surgery, however after six weeks you should be mainly back to normal. You will be able to gradually increase walking distances and duration over this time. You can stop using crutches when you feel confident and steady on your feet. For most people this takes 2-4 weeks. Sometimes a single crutch can continue to be useful, such as when walking outdoors. You will need to have your wound checked 10 – 14 days after surgery. This can be done at Mr Gormack’s clinic rooms or by your own GP, depending on what is most convenient. Pain levels will steadily decrease. You should aim to stop taking strong pain relief such as tramadol or Oxycontin by two weeks post-surgery. Paracetamol or ibuprofen can be continued as needed for up to six weeks. You will have an appointment booked to see Mr Gormack at six weeks post-surgery. If there are any concerns earlier, call or email the clinic.

WHAT ARE THE RISKS OF SURGERY?

There are risks associated with any surgery. Modern knee replacement is a very safe and successful operation, and the chance of having a significant problem are very low. The main risks of surgery include:

  • Infection

  • Bleeding

  • Nerve damage or blood vessel damage

  • Numbness (everyone will have a numb patch of skin on the front of the knee after surgery)

  • Blood clots in the legs or lungs (DVT / PE)

  • Stiffness

  • Fracture

  • Medical events after surgery such as heart attack, kidney injury, stroke, pneumonia

  • Wear or loosening of the knee implants.

WHAT ACTIVITIES CAN I DO / NOT DO AFTER SURGERY?

You will be able to gradually increase your activity level as you recover from surgery. You can walk on your new knee immediately after surgery, and stop using crutches as soon as you feel confident. Walking distances can increase over the next few months. You can start swimming and using an exercise bike after six weeks, and resume outdoor cycling after 8-12 weeks. With time you should be able to return to a full active lifestyle including regular walking, and sporting activities such as golf, tennis, cycling and skiing. While it is possible to run on your new knee, regular jogging is not recommended as this can cause premature wear and tear of the implants. While excellent range of motion is possible after knee replacement, most people are unable to bend their knee enough to allow deep squatting. The amount of movement in your knee is highly dependent on how stiff it was before surgery. Kneeling is often uncomfortable and needs to be done on soft surfaces; alternatively try using knee pads or a cushion to protect the front of your knee when kneeling.

WHEN CAN I DRIVE?

In order to drive safely you need to be able to control your vehicle and react quickly in the event of an emergency. For most people, this takes around six weeks after knee replacement surgery. If you have had a left knee replacement and drive an automatic car, driving may be possible between 4-6 weeks post-surgery. If you drive before this time you may not be covered by your insurance provider and may be liable in the case of an accident.

WHEN CAN I RETURN TO WORK?

Every job is different, so returning to work depends on the particular physical requirements of your employment. Most people will take around six weeks to return to work, although occasionally those with a sedentary job may return to work earlier. If you have a job that requires a lot of standing and walking then you may take 8 - 12 weeks to return to work. If your job is very physically demanding then expect to take 3 - 6 months to return to full duties, although light duties are generally possible earlier than this. Mr Gormack can give you a recommendation about the best time to return to work after discussing your individual circumstances and requirements.

HOW LONG WILL MY KNEE REPLACEMENT LAST?

Modern knee replacement implants are very durable, and generally last a long time. In New Zealand over 90% of knee replacements will last more than 10 years, and over 70% will last more than 20 years. Your age, size and activity level will determine how long your new knee will last. If you are over 65 years old when you have a knee replacement, there is a very high chance that this will last for the rest of your life. If you are very young, or place excessive load on your implants from heavy physical activity or excessive weight, your knee implant may not last as long. If your knee replacement wears out it is usually possible for it to be revised (re-done). Revision surgery is often challenging, and the results of a revision knee surgery are seldom as good as the first one.

WILL I SET OFF METAL DETECTORS AT THE AIRPORT?

Knee replacement implants are mainly metal. This means that they will set off the metal detectors at most airports. As knee replacement surgery is very common, airport security staff are accustomed to seeing people with artificial joints. There is no need to carry documentation with you; simply tell the airport security staff that you have an artificial knee, and they will confirm this with a hand held scanner.