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Knee replacement

Have you injured your knee or have a long-term knee problem?

The Bupa knee clinic can help you find the information and support you need.

Visit the Bupa knee clinic

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Knee replacement (sometimes called knee arthroplasty) involves replacing your knee joint if it’s painful and has been damaged or worn away, usually by arthritis or an injury.

You will meet the surgeon carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

How a knee replacement is carried out

About knee replacement

Your knee joint is made up by the lower end of your thigh bone (femur) and the upper end of your shin bone (tibia). These normally glide over each other easily because they are covered by smooth cartilage. If your cartilage is damaged by injury or worn away by arthritis, it can make your joint painful and stiff

Illustration of the different parts of the knee

A new knee joint will usually improve your mobility and reduce pain, although your new knee won’t be able to bend quite as far as a normal knee joint.

Depending on the condition of your knee joint, you may need to have part, or all, of your knee joint replaced. If you have arthritis just in one area of your knee joint, usually the inside part of the joint called the medial compartment, you may be offered a partial knee replacement (called a unicondylar knee replacement). However, a total knee replacement is more common.

Artificial knee parts are almost always made of metal (on the femur side) and plastic (on the tibia side) and a knee replacement can last for up to 20 years.

What are the alternatives to knee replacement?

Your surgeon will usually only recommend that you have surgery if non-surgical treatments, such as physiotherapy and exercise, medicines or using physical aids like a walking stick, no longer help to reduce your pain or improve your mobility.

Alternative surgical procedures include:

  • arthroscopy (if the arthritis isn’t too severe)
  • osteotomy (where your leg bones are cut and re-set)

You may have already had these procedures before your knee replacement. Your surgeon will explain your options to you.

Preparing for a knee replacement

Your surgeon will explain how to prepare for your knee replacement operation. For example, if you smoke you will be asked to stop, as smoking increases your risk of getting a chest and wound infection, which can slow your recovery.

The operation usually requires a hospital stay of about two to five days and can be done under general anaesthesia. This means you will be asleep during the operation. Alternatively you may prefer to have the surgery under spinal or epidural anaesthesia. This completely blocks feeling from your waist down and you will stay awake during the operation.

If you’re having a general anaesthetic, you will be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand. However, it’s important to follow your anaesthetist’s advice.

Your surgeon will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.

You may be asked to wear a compression stocking on your unaffected leg to help prevent blood clots forming in the veins in your legs. You may need to have an injection of an anticlotting medicine called heparin as well as, or instead of, wearing compression stockings.

What happens during a knee replacement?

A knee replacement usually takes one to two hours.

Your surgeon will make a single cut (10 to 30cm long) down the front of your knee. He or she will move your kneecap to one side to reach your knee joint. Your surgeon will remove the worn or damaged surfaces from both the end of your thigh bone and the top of your shin bone. He or she will usually remove some of the ligaments inside your knee but will leave the ones on the outside. Your surgeon will then shape the surfaces of your thigh and shin bones to fit the artificial knee joint and then fit the new joint over both bones.

Your surgeon may also replace the back of your kneecap with a plastic part. This is called patellar resurfacing.

After your surgeon has fitted the new joint, he or she will close your wound with stitches or clips and cover it with a dressing. Your surgeon will tightly bandage your knee to help minimise swelling.

What to expect afterwards

You will need to rest until the effects of the anaesthetic have passed. You may not be able to feel or move your legs for several hours after a spinal or epidural anaesthetic.

You may need pain relief to help with any discomfort as the anaesthetic wears off.

For the first day or so, you may have to wear special pads, attached to an intermittent compression pump, on your lower legs. The pump inflates the pads and encourages healthy blood flow in your legs and helps to prevent deep vein thrombosis (DVT). You may also be wearing a compression stocking on your unaffected leg to help maintain circulation.

A physiotherapist (a specialist in movement and mobility) will guide you daily through exercises to help your recovery.

You may also use a continuous passive motion exercise machine that will slowly bend and straighten your knee while you’re in bed, to restore movement and reduce swelling.

You will stay in hospital until you can walk safely with the aid of sticks, crutches or a walking frame. When you’re ready to go home, you will need to arrange for someone to drive you.

Your nurse will give you some advice about caring for your knee and a date for a follow-up appointment before you go home.

The amount of time your dissolvable stitches will take to disappear depends on the type of stitches you have. However, for this procedure, they should usually disappear in about six weeks. Non-dissolvable stitches and clips will be removed around 10 to 14 days after surgery.

Recovering from knee replacement surgery

It usually takes around six to 12 weeks to make a full recovery from knee replacement surgery, but this varies between individuals, so it's important to follow your surgeon's advice. Your knee will continue to improve for two years after your operation as scar tissue heals and your muscles get stronger through exercise.

If you need pain relief, you can take over-the-counter painkillers such as paracetamol or ibuprofen. Always read the patient information leaflet that comes with the medicine and if you have any questions, ask your pharmacist for advice.

Physiotherapy exercises are a crucial part of your recovery, so it's essential that you continue to do them for at least two months.

You should be able to move around your home and manage stairs but you will find some routine daily activities, such as shopping, difficult for a few weeks. You may need to use a walking stick or crutches for up to six weeks.

You may be asked to wear compression stockings for several weeks at home. When you’re resting, raise your leg and support your knee to help prevent swelling in your leg and ankle.

If you work, you should be able to return after six to eight weeks but this will depend on the type of work you do. Most people can drive after about four to six weeks after the operation but it’s important to follow your surgeon's advice.

What are the risks?

As with every procedure, there are some risks associated with knee replacement surgery. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your surgeon to explain how these risks apply to you.

Side-effects

These are the unwanted but mostly temporary effects you may get after having the procedure.

Your knee will feel sore and may be swollen for up to six months.

You will have a scar over the front of your knee. You may not have any feeling in the skin around your scar. This can be permanent, but should improve over two years.

Complications

Complications are when problems occur during or after the operation. The possible complications of any operation include an unexpected reaction to the anaesthetic, excessive bleeding or developing a blood clot, usually in a vein in the leg (DVT).

Complications of knee replacement can include:

  • infection of the wound or joint – your surgeon will give you antibiotics during and after surgery to help prevent this
  • an unstable joint – your knee joint may become loose and you may require further surgery to correct this
  • a dislocated kneecap – you will need another operation to repair this
  • damage to nerves or blood vessels (this is usually mild and temporary)
  • scar tissue, which can build up and restrict your movement – you may need further surgery to correct this

The artificial knee joint usually lasts for about 20 years, after which you may need to have another operation to replace it.


Produced by Rachael Mayfield-Blake, Bupa Health Information Team, October 2012.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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