Knee replacement

Knee replacement surgery (arthroplasty) is a common operation that involves replacing a damaged, worn or diseased knee with an artificial joint.

Adults of any age can be considered for a knee replacement, although most are carried out on people between the ages of 60 and 80.

A smaller operation called a partial knee replacement tends to be performed on younger people aged between 55 and 64 where the artificial joint is expected to need redoing within 10 years.

When a knee replacement is needed

Knee replacement surgery is usually necessary when the knee joint is worn or damaged so that your mobility is reduced and you are in pain even while resting.

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

• rheumatoid arthritis
• haemophilia
• gout
• disorders that cause unusual bone growth
• death of bone in the knee joint following blood supply problems
• knee injury
• knee deformity with pain and loss of cartilage

Who is offered knee replacement surgery

A knee replacement is major surgery, so is normally only recommended if other treatments, such as physiotherapy or steroid injections, have not reduced pain or improved 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're feeling depressed because of the pain and lack of mobility
• you cannot work or have a social life

You'll also need to be well enough to cope with both a major operation and the rehabilitation afterwards.

Types of knee replacement surgery

There are 2 main types of surgery:

• total knee replacement – both sides of your knee joint are replaced
• partial (half) knee replacement – only 1 side of your joint is replaced in a smaller operation with a shorter hospital stay and recovery period

Other surgery options

There are other types of surgery which are an alternative to knee replacement, but results are often not as good in the long term. Your doctor will discuss the best treatment option with you. Other types of surgery may include:

• arthroscopic washout and debridement – a tiny telescope (arthroscope) is inserted into the knee, which is then washed out with saline to clear any bits of bone or cartilage
• osteotomy – the surgeon cuts the shin bone and realigns it so that your weight is no longer carried by the damaged part of the knee
• mosaicplasty – a keyhole operation that involves transferring plugs of hard cartilage, together with some underlying bone from another part of your knee, to repair the damaged surface

Preparing for knee replacement surgery

Before you go into hospital, find out as much as you can about what's involved in your operation. Your hospital should provide written information or videos.

Stay as active as you can. Strengthening the muscles around your knee will aid your recovery. If you can, continue to do gentle exercise, such as walking and swimming, in the weeks and months before your operation. You can be referred to a physiotherapist, who will give you helpful exercises.

Read about preparing for surgery, including information on travel arrangements, what to bring with you and attending a pre-operative assessment.

Recovering from knee replacement surgery

You'll usually be in hospital for 3 to 5 days, but recovery times can vary. 

Once you're able to be discharged, your hospital will give you advice about looking after your knee at home. You'll need to use a frame or crutches at first and a physiotherapist will teach you exercises to help strengthen your knee.

Most people can stop using walking aids around 6 weeks after surgery, and start driving after 6 to 8 weeks. 

Full recovery can take up to 2 years as scar tissue heals and your muscles are restored by exercise. A very small amount of people will continue to have some pain after 2 years.

Risks of knee replacement surgery

Knee replacement surgery is a common operation and most people do not have 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
• 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
• deep vein thrombosis (DVT)
• persistent pain in the knee
• a break in the bone around the knee replacement during or after the operation

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

The National Joint Registry

The National Joint Registry (NJR) collects details of knee replacements done in England and Wales. Although it's voluntary, it's worth registering. This enables the NJR to monitor knee replacements, so you can be identified if any problems emerge in the future.

The registry also gives you the chance to participate in a patient feedback survey.

It's confidential and you have a right under the Freedom of Information Act to see what details are kept about you.

Page last reviewed: Tue Aug 2022 Next review due: Tue Aug 2022