Knee replacement surgery

What is knee replacement surgery?

Knee replacement surgery repairs damaged arthritic knee joints using an artificial knee joint, which helps to restore movement in the knee.

During knee replacement surgery the damaged and worn surfaces of the knee joint are carefully removed and resurfaced with a cobalt/chrome metal joint that is sized to fit. High density polyethylene (a type of plastic) sits between the metal surfaces and acts as a bearing surface. The back of the kneecap is also usually resurfaced with the same material.

Knee replacements usually last at least ten to fifteen years and will return you to normal movement and activity levels with less pain.

When might a knee replacement be necessary?

The most common type of arthritis is osteoarthritis, where there is gradual wear and tear of a joint. Arthritis eventually wears away the normal cartilage covering the surface of the joint and the bone underneath becomes damaged. Where this occurs in the knee, your consultant may recommend a knee replacement.

What does knee replacement surgery involve?

Knee replacement surgery is carried out in hospital under general anaesthetic although most people also have a spinal anaesthetic to make the legs completely painless for a few hours. You would normally be admitted the evening before the operation if your operation is in the morning or early on the day if your operation is scheduled for the afternoon or the evening. This allows you time to settle in and be prepared.

You will not be able to eat for eight hours prior to surgery although you will be able to drink small amounts of water up to four hours before.

The operation itself takes up to 90 minutes and your surgeon will make a 15 to 30 cm cut down the front of your knee. The kneecap is moved to one side so that the joint can be reached. Once the joint has been replaced the incision is closed with stitches or clips. An acrylic cement is usually used to bond the new joint directly onto your bones.

Afterwards your knee will be tightly bandaged to help minimise swelling and fine drainage tubes may also be left in for up to 48 hours.

Knee replacement surgery recovery time

You are likely to stay in hospital for up to four days after the operation and your physiotherapists will give you exercises that help you walk the day after the operation. You will gradually progress from using crutches to using walking sticks and you will be allowed to go home once you are fully weight bearing and can manage stairs and to care for yourself.

The knee dressing can be peeled off easily ten days after the surgery and, as the stitches are internal, they do not need to be removed. You will be given a cold compress or 'Cryocuff' along with instructions on how to cool your knee, which is important and aids recovery. You will see your consultant once again six weeks after your operation to review your progress.

Knee replacement surgery is a major operation and recovery takes place over 6 to 12 weeks. At six weeks, some patients will still be using a walking stick but most are walking well and independently at twelve weeks although you may not see the full benefit of surgery for up to a year.

What risks should I know about?

Knee replacement surgery is a very successful operation but there are some potential complications you should be aware of. These only affect less than 4% of patients.

  • Infection can occur although our theatres have ultra-clean air operating conditions keeping infection rates at 1-2%.
  • Blood clots are possible in any major joint replacement surgery but again are in the 1-4% category and have well-established treatments including aspirin
  • A small patch of numb skin can be present on the outer part of the knee near the kneecap, this will improve over time.
  • The knee will have some stiffness after the operation although we are aiming for 0-125 degs of movement once things have settled down.

Download our patient guide for knees booklet. 

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