Knee Replacement

This factsheet is for people who are considering having a knee replacement operation. Your care may differ from what is described here because it is adapted to meet your individual needs.

What does the operation involve?

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

The 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.

Types of artificial knee

There are several different types of artificial knee parts available commercially

Most 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 10-20 years, after which it may need to be replaced.

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. This is not always possible to perform.

Preparing for the operation

It is ideal to lose weight before a knee replacement operation. This makes the operation easier for the surgeon to perform as well as makes it more likely to succeed.

Building up the quadriceps muscles with simple exercises makes it easier to recover movement and strength after surgery.

You will generally have a preassessment where a nurse will help assess your fitness for surgery a few days before surgery. This will involve a history being taken as well as some special tests such as an ECG and some blood tests to assess fitness for anaesthesia. A booklet may be provided which is useful to read.

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 must not chew gum for at least 6 hours before surgery. 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).

The operation

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 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. You may have a urinary catheter for a day or two after surgery.

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.

You must move your feet regularly to keep the circulation going and prevent a clot in the leg veins.

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. It may be difficult for you to kneel on the knee after surgery.

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. Occasionally surgery is required to clean out any infection. If this does not resolve the infection the knee prosthesis may need to be removed and the joint cleaned out before putting in another one after the infection has resolved.
• Very rarely, nerves or blood vessels 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. In general the movement that is achieved after a knee replacement is not much more than the preoperative range of movement. • 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.
• Sometimes pain after this procedure may not completely resolve. This happens in upto 10% of patients who have this operation.

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.

If you have any particular concerns, please discuss these with Mr. Bajekal during your consultation or telephone the office on 02083677007