Knee Replacement

Knee replacement surgery also known as Knee Arthroplasty can help relieve pain and restore function in severely diseased knee joints. During knee replacement, a surgeon cuts away damaged bone and cartilage from your thighbone, shinbone and kneecap and replaces it with an artificial joint made of metal alloys, high-grade plastics and polymers.

Why is knee replacement surgery needed?

The most common reason for knee replacement surgery is osteoarthritis. Other conditions that cause knee damage include:

  • rheumatoid arthritis
  • hemophilia
  • gout
  • knee injury

Knee replacement is a major surgery, so is normally only recommended if other treatments, such as physiotherapy or steroid injections, haven’t helped reduce pain or improve mobility. You may be offered knee replacement surgery if:

  • you have severe pain, swelling and stiffness in your knee joint and your mobility is reduced
  • your knee pain is so severe that it interferes with your quality of life and sleep
  • everyday tasks, such as shopping or getting out of the bath, are difficult or impossible
  • you cannot work nor have a normal social life

Types of Knee Replacement Implants

In knee replacement surgery (arthroplasty), a damaged, worn or diseased knee is replaced with an artificial joint. Knee replacement is a routine operation for knee pain when the knee joint has been severely damaged, most commonly by arthritis. There are two main types of surgery, depending on the condition of the knee:

  • Total knee replacement
  • Partial (half) knee replacement

How is the operation carried out?

Modern knee replacements involve removing the worn ends of the bones in your knee joint and replacing them with metal and plastic parts (prosthesis). You may have either a total or a half-knee replacement. This will depend on how damaged your knee is. Total knee replacements are the most common.

Total Knee Replacement Procedure

In a total or full knee replacement, both sides of your knee joint are replaced. The procedure takes one to three hours:

  • Your surgeon makes a cut down the front of your knee to expose your kneecap. This is then moved to the side so the surgeon can get to the knee joint behind it.
  • The damaged ends of your thigh bone (femur) and shin bone (tibia) are carefully cut away. The ends are precisely measured and shaped to fit the appropriately sized prosthetic replacement. A dummy joint is positioned to test that the joint is working properly. Adjustments are made, the bone ends are cleaned, and the final prosthesis is fitted.
  • The end of your femur is replaced by a curved piece of metal, and the end of your tibia is replaced by a flat metal plate. These are fixed using special bone ‘cement’, or are treated to encourage your bone to fuse with the replacement parts. A plastic spacer is placed between the pieces of metal. This acts like cartilage, reducing friction as your joint moves.
  • The wound is closed with either stitches or clips. A dressing is applied to the wound, and sometimes a splint is used to keep your leg immobile.

Partial (half) Knee Replacement

If only one side of your knee is damaged, you may be able to have a partial (half) knee replacement. This is suitable for around one in four people with osteoarthritis..

Candidates for knee replacement surgery

Adults of any age can be considered for a knee replacement, although it’s typically recommended for older people as young, physically active people are more likely to wear the joint out. The earlier you have a knee replacement, the greater the chance you will eventually need further surgery. However, there is some evidence that replacing the knee joint before it becomes very stiff leads to a better outcome. Most total knee replacements are carried out on people between the ages of 60 and 80. You will need to be well enough to cope with both a major operation and the rehabilitation afterwards. Read more about getting ready for knee replacement surgery and recovering from knee replacement surgery.


Knee replacement surgery is a common operation and most people do not experience complications. However, as with any operation, there are risks as well as benefits. Complications are rare but can include:

  • stiffness of the knee
  • infection of the wound
  • deep infection of the joint replacement, needing further surgery
  • unexpected bleeding into the knee joint
  • ligament, artery or nerve damage in the area around the knee joint
  • blood clots or deep vein thrombosis (DVT)

In some cases, the new knee joint may not be completely stable and further surgery may be needed to correct it..