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Knee replacement

Knee replacement (sometimes called knee arthroplasty) involves replacing your knee joint if it’s painful and has been damaged or worn away, usually by arthritis or an injury.

You will meet the surgeon carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

Your knee joint is made up by the lower end of your thigh bone (femur) and the upper end of your shin bone (tibia). These normally glide over each other easily because they are covered by smooth cartilage. If your cartilage is damaged by injury or worn away by arthritis, it can make your joint painful and stiff.

A new knee joint will usually improve your mobility and reduce pain, although your new knee won’t be able to bend quite as far as a normal knee joint.

Depending on the condition of your knee joint, you may need to have part, or all, of your knee joint replaced. If you have arthritis just in one area of your knee joint, usually the inside part of the joint called the medial compartment, you may be offered a partial knee replacement (called a unicondylar knee replacement). However, a total knee replacement is more common.

Artificial knee parts are almost always made of metal (on the femur side) and plastic (on the tibia side) and a knee replacement can last for up to 20 years.

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Knee replacement surgery
How the operation is carried out
An image showing the different parts of the knee


  • Preparation Preparing for a knee replacement

    Your surgeon will explain how to prepare for your knee replacement operation. For example, if you smoke you will be asked to stop, as smoking increases your risk of getting a chest and wound infection, which can slow your recovery.

    The operation usually requires a hospital stay of about two to five days and can be done under general anaesthesia. This means you will be asleep during the operation. Alternatively you may prefer to have the surgery under spinal or epidural anaesthesia. This completely blocks feeling from your waist down and you will stay awake during the operation.

    If you’re having a general anaesthetic, you will be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand. However, it’s important to follow your anaesthetist’s advice.

    Your surgeon will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.

    You may be asked to wear a compression stocking on your unaffected leg to help prevent blood clots forming in the veins in your legs. You may need to have an injection of an anticlotting medicine called heparin as well as, or instead of, wearing compression stockings.

    An image showing the different parts of the knee 

    Bupa On Demand: Knee arthroscopy

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  • Alternatives What are the alternatives to knee replacement?

    Your surgeon will usually only recommend that you have surgery if non-surgical treatments, such as physiotherapy and exercise, medicines or using physical aids like a walking stick, no longer help to reduce your pain or improve your mobility.

    Alternative surgical procedures include:

    • arthroscopy (if the arthritis isn’t too severe)
    • osteotomy (where your leg bones are cut and re-set)

    You may have already had these procedures before your knee replacement. Your surgeon will explain your options to you.

  • The procedure What happens during a knee replacement?

    A knee replacement usually takes one to two hours.

    Your surgeon will make a single cut (10 to 30cm long) down the front of your knee. He or she will move your kneecap to one side to reach your knee joint. Your surgeon will remove the worn or damaged surfaces from both the end of your thigh bone and the top of your shin bone. He or she will usually remove some of the ligaments inside your knee but will leave the ones on the outside. Your surgeon will then shape the surfaces of your thigh and shin bones to fit the artificial knee joint and then fit the new joint over both bones.

    Your surgeon may also replace the back of your kneecap with a plastic part. This is called patellar resurfacing.

    After your surgeon has fitted the new joint, he or she will close your wound with stitches or clips and cover it with a dressing. Your surgeon will tightly bandage your knee to help minimise swelling.

    Knee replacement surgery
    Play video
    Knee replacement surgery
    How the operation is carried out
  • Knee replacement treatment on demand

    You can access a range of our health and wellbeing services on a pay-as-you-go basis, including knee replacements.

  • Aftercare What to expect afterwards

    You will need to rest until the effects of the anaesthetic have passed. You may not be able to feel or move your legs for several hours after a spinal or epidural anaesthetic.

    You may need pain relief to help with any discomfort as the anaesthetic wears off.

    For the first day or so, you may have to wear special pads, attached to an intermittent compression pump, on your lower legs. The pump inflates the pads and encourages healthy blood flow in your legs and helps to prevent deep vein thrombosis (DVT). You may also be wearing a compression stocking on your unaffected leg to help maintain circulation.

    A physiotherapist (a specialist in movement and mobility) will guide you daily through exercises to help your recovery.

    You may also use a continuous passive motion exercise machine that will slowly bend and straighten your knee while you’re in bed, to restore movement and reduce swelling.

    You will stay in hospital until you can walk safely with the aid of sticks, crutches or a walking frame. When you’re ready to go home, you will need to arrange for someone to drive you.

    Your nurse will give you some advice about caring for your knee and a date for a follow-up appointment before you go home.

    The amount of time your dissolvable stitches will take to disappear depends on the type of stitches you have. However, for this procedure, they should usually disappear in about six weeks. Non-dissolvable stitches and clips will be removed around 10 to 14 days after surgery.

  • Recovery Recovering from knee replacement surgery

    It usually takes around six to 12 weeks to make a full recovery from knee replacement surgery, but this varies between individuals, so it's important to follow your surgeon's advice. Your knee will continue to improve for two years after your operation as scar tissue heals and your muscles get stronger through exercise.

    If you need pain relief, you can take over-the-counter painkillers such as paracetamol or ibuprofen. Always read the patient information leaflet that comes with the medicine and if you have any questions, ask your pharmacist for advice.

    Physiotherapy exercises are a crucial part of your recovery, so it's essential that you continue to do them for at least two months.

    You should be able to move around your home and manage stairs but you will find some routine daily activities, such as shopping, difficult for a few weeks. You may need to use a walking stick or crutches for up to six weeks.

    You may be asked to wear compression stockings for several weeks at home. When you’re resting, raise your leg and support your knee to help prevent swelling in your leg and ankle.

    If you work, you should be able to return after six to eight weeks but this will depend on the type of work you do. Most people can drive after about four to six weeks after the operation but it’s important to follow your surgeon's advice.

    Exercises to strengthen your knee 

  • Risks What are the risks?

    As with every procedure, there are some risks associated with knee replacement surgery. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your surgeon to explain how these risks apply to you.


    These are the unwanted but mostly temporary effects you may get after having the procedure.

    Your knee will feel sore and may be swollen for up to six months.

    You will have a scar over the front of your knee. You may not have any feeling in the skin around your scar. This can be permanent, but should improve over two years.


    Complications are when problems occur during or after the operation. The possible complications of any operation include an unexpected reaction to the anaesthetic, excessive bleeding or developing a blood clot, usually in a vein in the leg (DVT).

    Complications of knee replacement can include:

    • infection of the wound or joint – your surgeon will give you antibiotics during and after surgery to help prevent this
    • an unstable joint – your knee joint may become loose and you may require further surgery to correct this
    • a dislocated kneecap – you will need another operation to repair this
    • damage to nerves or blood vessels (this is usually mild and temporary)
    • scar tissue, which can build up and restrict your movement – you may need further surgery to correct this

    The artificial knee joint usually lasts for about 20 years, after which you may need to have another operation to replace it.

  • FAQs FAQs

    How long will my knee replacement last?


    Almost all knee replacements last at least 10 or 15 years, and some as long as 20 years.


    Replacement joints are designed to last for a long time. The modern materials that are used are strong enough to stand up to the requirements of young and active people.

    Currently, about eight or nine out of 10 artificial joints used for knee replacement last for 20 years or more. However, there is increasing research into the design and material of replacement knee joints to make them last longer.

    It’s important to have an X-ray on your knee at least every five years after your operation. If your replacement joint is loosening or breaking, you may need another operation to correct this.

    Are there any sports or activities I shouldn't take part in after my knee replacement?


    Once you’re fully recovered, you can exercise and participate in sport. However, this excludes high-impact exercises, such as running and jumping.


    During your recovery your physiotherapist will recommend exercises for you that will improve your strength and range of motion. It’s important to do these for at least two months after your operation.

    As you recover, you can start swimming and do more walking to strengthen your muscles around the joint. You can gradually start cycling but if you feel any pain than you must stop and allow yourself more time to recover.

    When you have made a full recovery, you can have a more active lifestyle. However it's important that you don't take part in high-impact activities or contact sports. So don’t do sports such as football, rugby, basketball, squash, skiing or anything that involves squats, jumping or weightlifting. But you can do low-impact sports such as golf, bowls or gentle doubles tennis or dancing.

    Regular exercise will help to improve and maintain your mobility. When returning to any sport it's important to take your time to rebuild your strength and co-ordination.

    You may find that you can't return to your chosen sport at the same level as you were before. Your risk of injury is greatly increased if you take part in competitive, rather than recreational, sport.

    Your doctor, surgeon or physiotherapist will be able to give you more information about what activities are suitable.

    What can I do to make my recovery easier?


    Try to be as fit and healthy as possible before your operation and prepare your home for when you return.


    If you’re having a knee replacement it's a good idea to try to be as fit and healthy as possible before your operation to speed up your recovery.

    If you smoke you will be asked to stop, as smoking can increase your chances of getting a wound infection and slows your recovery. If you’re overweight, your doctor may recommend a weight-loss programme.

    You can exercise to strengthen your upper body. This will help you to get around after the surgery when using walking aids such as crutches.

    If possible, try to strengthen your leg muscles. Strengthening the muscles around your knee will speed your recovery and will make it easier to perform the postoperative exercises. Your surgeon or physiotherapist will be able to recommend exercises for you.

    It's a good idea to prepare your home for when you return from hospital. This may mean rearranging furniture to make it easier to move around, and placing commonly used items at arm level so you don't have to reach for them. It's also a good idea to stock up on non-perishable food such as frozen or tinned items, so that you don't need to go shopping immediately after your surgery.

    You may need someone to help during the first few weeks after surgery. It's a good idea to arrange to have a friend or family member stay with you for a couple of days after the operation.

    What is the difference between a partial and a total knee replacement?


    A total knee replacement will replace all of the surfaces of your knee joint whereas a partial knee replacement will replace just part of your knee joint, for example just the inner side of your joint. A total knee replacement is more common.


    If you have a total knee replacement, your surgeon will replace the surface at the end of your thigh bone (femur) and the surface of the top of your shin bone (tibia). He or she may also replace the surface of your kneecap (patella).

    Sometimes, for people with osteoarthritis for example, just one side of the knee is affected so it isn’t necessary to replace the entire joint. In this operation, your surgeon will replace the surface on just one side of your joint in a partial knee replacement – sometimes called a unicompartmental knee replacement. Your surgeon will only replace the damaged part of your knee joint with metal and/or plastic and will leave the healthy cartilage and bone in the rest of your knee.

    It may be possible for your surgeon to do a partial knee replacement through a smaller cut than a total knee replacement. This can shorten the time you need to stay in hospital and you may recover faster. However, a partial knee replacement operation isn’t suitable for everybody – you will need to have strong, healthy ligaments within your knee. Ask your surgeon if it’s an option for you.

    It’s also possible that a partial knee replacement won’t be successful in the long term, and you may need to have a total knee replacement a few years later.

  • Resources Resources

    Further information


    • Total knee arthroplasty. eMedicine., published 27 June 2012
    • Total knee replacement. American Academy of Orthopaedic Surgeons., published December 2011
    • Knee replacement. Arthritis Research UK., published April 2011
    • Mini-incision surgery for total knee replacement. National Institute for Health and Clinical Excellence., published 11 February 2011
    • Hochberg MC, Altman RD, April KT. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care and Research 2012; 64(4):465–74. doi:10.1002/acr.21596.
    • Total joint replacement rehabilitation. eMedicine., published 16 April 2012
    • Surgery and arthritis. Arthritis Care., published April 2010
    • Harvey LA, Brosseau L, Herbert RD. Continuous passive motion following total knee arthroplasty in people with arthritis. Cochrane Database of Systematic Reviews 2010, Issue 3. doi:10.1002/14651858.CD004260.pub2
    • Activities after a knee replacement. American Academy of Orthopaedic Surgeons., accessed 22 October 2012
    • Adie S, Kwan A, Naylor JM, et al. Cryotherapy following total knee replacement. Cochrane Database of Systematic Reviews 2012, Issue 9. doi:10.1002/14651858.CD007911.pub2
    • ACR appropriateness criteria. American College of Radiology., published 2011
    • Preparing for joint replacement surgery. American Academy of Orthopaedic Surgeons., published January 2009
    • Unicompartmental knee replacement. American Academy of Orthopaedic Surgeons., published June 2010
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