Knee replacement

What it is

Knee replacement
Knee replacement

What is a knee replacement?

  • Knee replacement surgery involves replacing damaged parts of your knee joint with metal or plastic parts.
  • It's most commonly used to treat pain and stiffness in the knee joint caused by osteoarthritis.
  • It may be recommended if other treatments or lifestyle changes have not worked and knee pain is affecting your daily life.
  • Depending on the damage to your knee, it can be used to replace all of your knee joint (total knee replacement) or some of it (partial knee replacement).
  • You'll have the operation in hospital. It can take several months or more to fully recover afterwards.
  • Knee replacements can last for 20 years or more and can significantly improve daily life for people with knee pain.

Why it's done

Reasons for having a knee replacement

A knee replacement may be recommended if knee pain is having a big effect on your life and alternatives to a knee replacement have not worked.

Most people who have a knee replacement have pain and movement problems caused by osteoarthritis (a condition that causes joints to become painful and stiff).

Other conditions a knee replacement may be used to treat include gout and sports injuries, but this is not common.

The knee usually moves smoothly because the ends of the bones are covered with a layer of tough tissue called cartilage. If the cartilage is worn away by osteoarthritis or damaged by an injury, the bones rub against each other, making your joint painful and stiff.

During a knee replacement, the damaged parts of your knee are replaced with metal and plastic parts.

Knee replacements are usually very successful and result in no pain in the knee and better movement.


Common alternatives to a knee replacement

There are other treatments that may be tried before having a knee replacement, as well as other types of surgery that may help.

Treatments that may be tried first

Before having a knee replacement, your doctor will talk to you about non-surgical treatments to help with your knee pain.

These may include lifestyle changes and some types of pain relief, such as:

  • weight loss to reduce the strain on your knee if you're overweight
  • low-impact exercise such as swimming, walking or cycling, and muscle strengthening in the knee – a physiotherapist may advise and support you with exercising
  • using walking aids
  • wearing special footwear or insoles for your shoes
  • pain relief medicines, gels or creams
  • hydrocortisone (steroid) injections – an injection into the knee joint to help with pain and swelling

If you've tried these and they have not helped, your doctor may talk to you about surgery to repair or strengthen the knee or having a knee replacement.

Other types of surgery

Your doctor may talk to you about other types of surgery that do not involve a knee replacement if these are an option for you.

These are not suitable for everyone but might include:

  • arthroscopy – where fluid is flushed into the knee joint to clear out any loose bone and cartilage
  • osteotomy – where the shape of your shin bone is changed to reduce pressure on the worn or damaged part of your knee
  • microfracture – where small holes are made in the surface of the bone to help new cartilage grow


How to prepare for a knee replacement

Before your knee replacement, your doctor will talk to you about the things you can do to prepare.

This might include advice on:

  • exercises to do before and after that will help with your recovery
  • stopping smoking
  • having a healthy diet
  • managing your weight

It's important to do these things while you wait for your knee replacement, because waiting lists can be long. Following your doctor's advice will also help you recover as well as possible after surgery.

Pre-admission clinic

You might be asked to go to a pre-admission clinic a few weeks before the operation. This is to make sure you're well enough for it to go ahead.

It might involve having some tests such as a blood test and checking your blood pressure. You may also meet the healthcare team involved in your care so you can learn more about the operation and recovery afterwards, and ask any questions you might have.

Prepare for recovering at home

It's a good idea to prepare for when you get home after the operation.

You might want to think about:

  • asking for any help you might need at home with day-to-day activities
  • making sure things you use often are easy to reach
  • stocking your freezer with cooked meals
  • arranging transport, as you'll be unable to drive for several weeks after the operation
  • speaking to your employer and making a plan for returning to work if you need to

How is it performed?

What happens during a knee replacement

If you're having a knee replacement, you'll usually go into hospital on the day of the operation.

Just before the operation, a nurse will take you to the operating theatre.

You'll either have a general anaesthetic (you're asleep during the operation) or a local anaesthetic in your spine (you're awake but will have no feeling from the waist down).

The operation usually takes about 1 to 2 hours. The type of surgery you have depends on things like how damaged your knee is, your age and your general health.

Total knee replacement

A total knee replacement is the most common type of knee replacement. This is where the lower end of your thigh bone and the upper end of your shin bone are replaced with metal and plastic parts.

The main steps of a total knee replacement are:

  • The surgeon makes a cut down the front of your knee and moves your kneecap to the side so they can get to the knee joint behind it.
  • They cut away the damaged ends of your shin bone and thigh bone.
  • New parts are fitted over the ends of both bones to create the new joint. The parts are usually made of metal and plastic. Some people may also have the back of the kneecap replaced with a new part.
  • The kneecap is put back into place.
  • The surgeon closes the cut on your knee using stitches or clips and covers it with a dressing and bandage.
  • After the operation, you'll stay in a recovery room until you're fully awake, where you may be given medicines to help with the pain.

Partial knee replacement

A partial knee replacement is used when you have arthritis in one half of your knee. Only the bones on the affected side are replaced with metal or plastic parts.

It's a similar operation to a total knee replacement, but the cut on your knee will be smaller and you should have a quicker recovery.

National Joint Registry

After surgery, you'll be asked if you consent to giving your personal details and details of your knee replacement to the National Joint Registry (NJR).

The NJR collects and monitors details of knee replacements to help improve patient safety, experience and outcomes.


How to recover from a knee replacement

It may take several months or longer to fully recover from a knee replacement. This can vary depending on your age and general health.

Recovery for a partial knee replacement should be shorter than a total knee replacement.

It's important to follow the advice the hospital gives you on looking after your knee to have a good recovery.

Recovering in hospital

After the operation, you'll spend some time in a recovery room where you may be given medicines to help with the pain.

You'll continue to have painkillers in the days after the operation as your knee will be sore.

You'll have help from nurses and physiotherapists to start walking soon after the operation so you can go home as soon as possible. You'll need crutches or a walking frame at first.

Recovering at home

You can usually go home if your wound is healing well and you can safely get around. Most people can leave hospital 1 to 3 days after the operation.

Before you leave, a physiotherapist or occupational therapist will talk to you about managing daily activities and home exercise programmes. Following the exercises early on in your recovery will help with the long-term strength and movement in your knee.

A nurse will take out your stitches or clips after about 10 days. You'll also have a follow-up appointment about 6 weeks after the operation to check you're recovering well.


  • use crutches or walking sticks at first – go down to 1 crutch then a walking stick when you feel confident
  • try walking without an aid after about 6 weeks if you feel ready
  • get up and walk around for 5 minutes every hour to prevent blood clots
  • wait at least 6 weeks to drive again if you've had a total knee replacement or 3 weeks if you've had a partial knee replacement – check with your doctor that you're fit to drive
  • avoid twisting your knee, bending down and reaching up as much as possible
  • follow the exercises your physiotherapist has recommended
  • keep your leg raised as much as possible to reduce swelling
  • return to work when you feel ready – this is usually after about 6 to 12 weeks but will depend on the type of work you do


  • do not sit with your legs crossed for the first 6 weeks
  • do not sleep with a pillow under your knee (you do not need to sleep in a special position after the operation)
  • do not kneel on your new knee until your doctor says you can
  • do not stand for long periods of time as this could cause swelling in your ankles
  • do not do household tasks that involve lifting or moving anything heavy (like vacuuming) for the first 3 months


Possible complications of a knee replacement

A knee replacement is a common and safe procedure. However, as with any operation there are risks. Your doctor will explain these to you.

Most people who have a knee replacement have no complications. If there are any, they are usually minor and can be treated.

The risk of having complications depends on your age and general health.

Blood clots or DVT (deep vein thrombosis)

Blood clots or DVT (deep vein thrombosis) are possible after a knee replacement because of how the blood flows and clots after surgery. This is often not serious.

If you have a blood clot that causes pain or swelling, your doctor can give you anticoagulant medicines to help.

A blood clot that forms in the leg can sometimes travel to your lungs (pulmonary embolism). This can cause serious complications.

To reduce the risk of blood clots your doctor might suggest wearing compression stockings or taking anticoagulant medicines.

Wound infection

There's a small chance that your knee wound could get infected after the operation. This is usually treated with antibiotics.

If the infection spreads deep into the knee joint, you may need further surgery.

Damage to nerves or tissue

During surgery, there's a chance that a blood vessel, nerve or ligament around the knee joint could be damaged.

This is not common and can either be repaired during surgery or will heal afterwards.

Problems with your new knee

Most people find their daily life improves after a knee replacement. However, it's possible that you may have ongoing issues with your new knee, including:

  • problems bending the knee
  • ongoing pain and stiffness
  • the knee being unstable when you stand up or walk

Physiotherapy and certain exercises may help with these problems.

Most knee replacements last for about 20 years or more. Depending on when you had the operation you may need another replacement later in life, but this is not common.

Ask for an urgent GP appointment or get help from NHS 111 if:

You've recently had a knee replacement and you have:

  • throbbing or cramping pain in your leg
  • a high temperature
  • chills and feel shivery
  • oozing or pus from your wound
  • redness, tenderness, swelling or pain in your knee that is not getting better or is getting worse

These could be signs of an infection or a blood clot.

You can call 111 or get help from 111 online.

Call 999 or go to A&E if:

You have pain and swelling in your leg and:

  • you're having difficulty breathing
  • you have chest pains

This could be a blood clot in the lungs (pulmonary embolism), which needs to be treated immediately.

Find your nearest A&E

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 26/05/2023 10:48:11