As with any operation, knee replacement surgery has risks as well as benefits. Most people who have a knee replacement don't experience serious complications.

After having a knee replacement, contact your doctor if:

  • you develop hot, reddened, hard or painful areas in your legs in the first few weeks after your operation – although this may just be bruising from the surgery, it could mean a blood clot has developed
  • you experience chest pains or breathlessness – although it's very rare, you could have a clot on your lung (pulmonary embolism) which needs urgent treatment


Anaesthetics are extremely safe, but carry a risk of minor side effects such as sickness and confusion (usually temporary). There is also a slight risk of serious complications.

The risk of death in a healthy person having routine surgery is very small. Death occurs in around one in every 100,000 general anaesthetics given.

The risk is higher if you're older or have other health conditions, such as heart or lung disease.

Your anaesthetist and surgeon can answer questions you may have about your personal risks from anaesthetic or the surgery itself.

Other complications

Complications occur in about one in 20 cases, but most are minor and can be successfully treated. Possible complications include:

  • infection of the wound – this is usually treated with antibiotics, but occasionally the wound can become deeply infected and require further surgery; in rare cases it may require replacement of the artificial knee joint.
  • 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) – clots may form in the leg veins as a result of reduced movement in the leg during the first few weeks after surgery. They can be prevented by using special support stockings, starting to walk or exercise soon after surgery, and by using anticoagulant medicines
  • fracture in the bone around the artificial joint during or after surgery – treatment will depend on the location and extent of the fracture
  • excess bone forming around the artificial knee joint and restricting movement of the knee – further surgery may be able to remove this and restore movement
  • excess scar tissue forming and restricting movement of the knee – further surgery may be able to remove this and restore movement
  • the kneecap becoming dislocated – surgery can usually repair this
  • numbness in the area around the wound scar
  • allergic reaction – you may have an allergic reaction to the bone cement if this is used in your procedure

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

How long will a replacement knee last?

Wear and tear through everyday use means your replacement knee won't always last forever. Some people will need further surgery.

According to the National Joint Registry (NJR), around 5% of patients who have a knee replacement (1 in 20) will need further surgery after 12 years. However, this varies depending on the type of replacement. Total knee replacements tend to last longer than partial knee replacements.

Find more detailed information on how long knee implants last on the NJR website.

Page last reviewed: 25/07/2016
Next review due: 25/07/2019