Knee Replacement (through Operation)

A knee replacement operation involves replacing damaged or worn parts of the knee joint with a prosthesis made up of metal and plastic parts.

Your knee joint is made up by the ends of the thigh bone and shin bone, which normally glide over each other smoothly because they are covered by shock-absorbing articular cartilage. If the cartilage is damaged by injury or worn away by arthritis, for example, it can make the joint painful and stiff. A new knee joint can help improve mobility and reduce pain.

Depending on the condition of your knee, a total or a half knee replacement may be done. In a half knee operation, only the inner or outer half of your knee is replaced. A total knee replacement is more common.

Types of artificial knee
There are several different types of artificial knee parts.

Some artificial knee parts need special cement to keep them in place. Others are coated with a chemical which encourages bone to grow into it to hold the components in place. A cemented knee replacement usually lasts for at least 10 years, after which it may need to be replaced.

Your surgeon will discuss the various options with you.

What are the alternatives ?
Surgery is usually recommended only if non-surgical treatments, such as taking medicines or using physical aids like a walking stick, no longer help to reduce pain or improve mobility.

There is an alternative procedure known as a single component knee replacement operation, which may help if only one side of your knee joint has worn down. Your surgeon will explain your options.

Preparing for your operation
Your doctor will discuss how to prepare for your operation. For example, if you smoke you may be asked to quit, as smoking will increase your risk of getting a chest or wound infection and slow your recovery.

What to expect in hospital
Before surgery you will talk to your surgeon about the operation and you will be asked to sign a consent form. This confirms that you understand the risks, benefits and possible alternatives to the procedure and have given your permission for it to go ahead.

You will also be asked to consent to placing your name on the National Joint Register, which is used to follow up the safety, durability and effectiveness of joint replacements.

If you are having a general anaesthetic, you will be asked to follow fasting instructions. Typically, you must not eat or drink for about six hours before a general anaesthetic. However, some anaesthetists allow occasional sips of water until two hours beforehand.

You may be asked to wear a compression stocking on the unaffected leg to help prevent blood clots forming in the veins (deep vein thrombosis, DVT).

A knee replacement usually takes up to two hours.

It is usually performed under a general anaesthetic. This means that you will be asleep during the procedure and will feel no pain. Alternatively, the surgery can be carried out under an epidural that completely blocks pain in the leg, but you will be awake.

Once the anaesthetic has taken effect, your surgeon will make a single cut (15 to 30cm long) down the front of your knee. The length of the cut may be shorter depending on the technique your surgeon is using.

Your kneecap will be moved to one side so the joint can be reached.

The worn or damaged surfaces will be removed from both the end of your thigh bone and the top of your shin bone. The surfaces will then be shaped to fit the knee replacement. The replacement joint will be fitted over both bones.

Sometimes the back of your kneecap is replaced with a plastic prosthesis. This is called patellar resurfacing.

After the new parts are fitted, the wound is closed with stitches or clips and covered with a dressing. Your knee will be tightly bandaged to help minimise swelling.

What to expect afterwards
You will be given painkillers to help relieve any discomfort as the general anaesthetic wears off. If you have an epidural anaesthetic, you may not be able to feel or move your legs for several hours after your operation. You won't have any pain either.

On the first day, you may have to wear special pads, attached to an intermittent compression pump, on your calves. The pump inflates the pads and encourages healthy blood flow in your legs and helps to prevent DVT.

Starting from the day after your operation, a physiotherapist will usually visit daily to help you with exercises designed to help your recovery.

You will be in hospital until you are able to walk safely with the aid of sticks or crutches. This will usually be 3 to 5 days after your operation.

Before going home, your nurse will give you advice about caring for your stitches, hygiene and bathing.

After you return home
Continue to take your painkillers if you need to, as advised by your surgeon.

You may be asked to wear compression stockings for several weeks at home. They are difficult to put on and take off, and you will need someone to help you with this.

The exercises recommended by your physiotherapist are a crucial part of your recovery, so it's essential that you continue to do them.

You will be able to move around your home and manage stairs. You will find some routine daily activities, such as shopping, difficult for a few weeks. When you are resting, you should rest with your leg raised to help prevent swelling in the leg and ankle.

Follow your surgeon's advice about driving. You shouldn't drive until you are confident that you could perform an emergency stop without discomfort.

Depending on the type of work you do, you can usually return to work after six to eight weeks.

What are the risks ?
A knee replacement is a commonly performed and generally safe surgical procedure. For most people, the benefits are far greater than the disadvantages. However, in order to make an informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications.

Side-effects
These are the unwanted but mostly temporary effects of a successful procedure. After surgery, your knee will be sore when you move it and swollen for up to three months.

You will have a scar over the front of the knee. The scar and the outer side of the knee may be numb, which can sometimes be permanent.

Complications
Complications are when problems occur during or after the procedure. Most people are not affected. The main complications of any operation are bleeding during or soon after the procedure, infection and an abnormal reaction to the anaesthetic. Some of the complications specific to a knee replacement are listed here.

* The wound or joint can get infected. Antibiotics are given during surgery to help prevent this.

* Sometimes it is not possible to make the new knee fully stable and you may need to have a second operation.

* The operated leg may be a slightly different length. Sometimes, a raised shoe on the shorter side is necessary.

* Very rarely, nerves in the leg can get damaged during the operation.

* A build-up of scar tissue occasionally restricts movement. Another operation may be performed to break down the scar tissue. In rare cases, the loss of movement may be permanent.

* The kneecap can become dislocated after surgery.

* It's possible to develop a blood clot in the veins of the leg (deep vein thrombosis, DVT). This clot can break off and cause a blockage in the lungs. It's usually treatable, but it can be a life-threatening condition. You will be given medicines and/or compression stockings to wear during the operation to help prevent DVT.

A knee replacement usually lasts for at least 10 to 15 years, after which you may need a repeat operation to replace it. However, repeat knee replacements are more complicated than original knee replacements, and the results are not always as successful.