Knee replacement
- Mr Damian McClelland, Trauma and Orthopaedic Consultant, and Clinical Director for Musculoskeletal Services at Bupa
- Rachael Mayfield-Blake, Freelance Health Editor
Knee replacement surgery is an operation to remove damaged parts of your knee joint and replace them with artificial ones. You may need to have a knee replacement if your knee is painful and parts have been damaged or worn away. This is usually because of osteoarthritis.
How knee replacement surgery is carried out
Knee replacement surgery | Watch in 1:52
Knee replacement can improve your quality of life and reduce your pain. Learn how the surgery is carried out here.
About knee replacement surgery
Your knee joint is made up of the lower end of your thigh bone (femur) and the upper end of your shin bone (tibia) and your knee cap (patella). These normally glide over each other easily because they’re covered by smooth cartilage. But if your cartilage is damaged by an injury or worn away by arthritis, this can make your joint painful and stiff.
A new knee joint should ease your pain and help you move around more easily, so you can be more active. But it may not be able to bend as much as a normal knee joint. Artificial knee parts are usually made from metal and plastic.
A knee replacement can last for up to 25 years but most last 15–20 years. Over 100,000 people have a knee replacement operation (total knee arthroplasty) each year in the UK. Most people who have knee replacement surgery are in their 70s.
Types of knee replacement surgery
There are two main types of knee replacement surgery.
- Total knee replacement (TKR), or total knee arthroplasty, is the most common. Your surgeon will replace the lower end of your thigh bone and the upper end of your shin bone with artificial parts. They may also replace the surface under your kneecap (patella) with a plastic button if this is damaged too.
- Partial knee replacement is called unicompartmental knee replacement (UKR). Your surgeon will replace the ends of the bones on one side of your knee only, usually the inside of your knee. They may make a smaller cut than with a TKR.
Your surgeon will discuss which type of surgery is right for you. It will depend on a number of things, such as the condition of your knee, your age, and your general health.
Preparation for knee replacement surgery
Home preparations
Before you have a knee replacement, make some preparations in advance for when you get home. For example, arrange for family or friends to help with things like cooking and shopping. And stock your freezer with some cooked meals. Make sure there’s nothing you could trip over while you’re less able to move around. Move things you’ll need to have at hand – for example, your medicines, books, and the TV remote control.
Pre-admission assessment
Your hospital may invite you to a pre-admission assessment clinic a few weeks before your operation to check that you’re fit for surgery. Let the team know if you’re taking any medicines. If you smoke, it’s best to stop because this will help you recover more quickly. If you haven’t managed to give up, don’t smoke – or vape – on the day of your operation. You may also need to lose some weight before your surgery if you’re overweight.
Advice for a general anaesthetic
A general anaesthetic can make you sick. This is why, if you’re having a general anaesthetic, it's important that you don't eat or drink anything before your procedure. Your hospital will advise you when you need to stop eating and drinking from. Follow your anaesthetist's advice. If you have any questions, just ask.
Compression stockings
You may need to wear compression stockings to help prevent blood clots forming in the veins in your legs (deep vein thrombosis). You may also need to have an injection of an anti-clotting medicine.
Your surgeon will tell you what will happen before, during, and after your surgery. If you’re unsure about anything, don’t be afraid to ask. No question is too small. It’s important that you feel fully informed so you feel happy to give your consent for the operation to go ahead. Your surgical team will ask you to sign a consent form.
Knee replacement surgery
A knee replacement usually takes anything from 45 minutes to over two hours.
There are two main options for anaesthesia for knee replacement surgery.
- Most people have knee replacement surgery under an epidural (spinal anaesthesia). Your surgeon will inject the anaesthetic into your back (between the bones of your spine). This will completely block any feeling from your waist down and you’ll stay awake during the operation. You can have this on its own or with a sedative to relax you.
- Another option is general anaesthesia, which means you’ll be asleep during the operation.
After your anaesthetic takes effect, your surgeon will make a cut down the front of your knee. They’ll then trim the worn or damaged surfaces from the end of your thigh bone and the top of your shin bone. They’ll 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 button-shaped part. This is called patella resurfacing.
After your surgeon has fitted the new joint, they’ll close your wound with stitches and cover it with a dressing.
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Aftercare for knee replacement surgery
You’ll need to rest until the effects of the anaesthetic have worn off. You might not be able to feel or move your legs for a few hours after a spinal anaesthetic.
Your nurse will give you painkillers to help with any discomfort as the anaesthetic wears off.
You’ll have a large dressing on your knee to protect your wound, and there may be one or more tubes coming out of it. These will help to drain any fluid that builds up around your wound. One of your hospital team will usually take the tubes out after a day or two.
You’ll probably be able to move your knee again a day after your surgery. If you start to move your knee within 24 hours, it may help you recover more quickly and get home sooner. A physiotherapist will give you some exercises to do. You may also use a continuous passive motion exercise machine. This will slowly bend and straighten your knee while you’re in bed to get your knee moving again and reduce any swelling.
You’ll stay in hospital for one to two days after your surgery, although it can sometimes be longer. Some hospitals offer knee surgery as a day case, which means you can have the operation and go home the same day. Your nurses will encourage you to walk as soon as possible, with the help of crutches or a walking frame.
Your nurse will give you advice about caring for your knee and a follow-up appointment date before you go home. Your physiotherapist or an occupational therapist will give you tips on how to carry out daily activities such as using the stairs or washing yourself. When you’re ready to go home, ask family or a friend to drive you.
Unless you have dissolvable stitches, you’ll need to have your stitches or staples taken out about 10 to 12 days after your operation. A nurse at your local GP surgery can do this for you.
Recovery for knee replacement surgery
It usually takes around 6 to 12 weeks for the early part of your recovery from knee replacement surgery. But you’ll continue to improve for up to a year as the healing continues. You may need some kind of pain relief during the early healing phase to help you move around. Physiotherapy is an essential part of your recovery. Gentle and regular exercise will help to prevent problems such as a stiff knee.
Any swelling in your knee, ankle, or foot after surgery can last for several months or more but should gradually get better. To help reduce the swelling, keep your foot raised. But remember to get up and have a walk around for five minutes in every hour to prevent blood clots. You can also put an ice pack on your knee, but wrap it in a towel so it doesn’t harm your skin.
During the first six weeks, it’s best not to sit with your legs crossed. After three months, you can try kneeling, but put a soft cushion down first. Kneeling shouldn’t damage your knee but you need to wait until the scar tissue has healed. Kneeling may never be entirely comfortable.
Try to build up your daily activities gradually. Here are some general timescales.
- You may need to use a walking stick or crutches for up to six weeks.
- By six to eight weeks, you may be able to go for a walk, cycle and swim, but check with your physiotherapist first.
- You won’t be able to drive for six to eight weeks after total knee replacement surgery, or around three weeks after a partial knee replacement. Follow your surgeon's advice and check your motor insurance.
- If you work, you should be able to go back after about six to eight weeks, depending on the type of work you do. If you have a physically demanding job, it may be up to 12 weeks before you’re ready. Ask your surgeon what they recommend.
You may feel tired and a bit emotional for a while after your surgery – this is normal. You’ve had a major operation and your body needs time to heal and recover.
Side-effects of knee replacement surgery
After knee replacement surgery, you may have some temporary side-effects.
- Pain – you’ll probably have some pain or discomfort in your knee. The pain may last for around 12 weeks, but can sometimes last longer. If you find it hard to ease your pain with painkillers or if it gets worse, see your GP.
- Swelling – it’s normal to get some swelling of your leg, ankle, and foot for the first few months or so after surgery. But if the swelling gets worse or your calf becomes painful it can be a sign of a blood clot and you’ll need urgent medical help.
- Scarring – you’ll have a scar down the front of your knee, about 10 to 18 cm (4 to 7 inches) long. You may not have any feeling in the skin around your scar for a while. This should get better over two years but it might not ever feel completely normal.
- Weakness – your leg may feel weak at first. But it will get stronger as you start exercising your muscles.
- Clicking. You may feel or hear some clicking in your new implant in your knee when you bend your knee or walk. This is normal.
Complications of knee replacement surgery
Possible complications after knee replacement surgery include the following.
- Blood clots – you could get a blood clot in the veins in your legs (deep vein thrombosis, DVT). You can help to prevent this by wearing compression stockings, staying active, and taking medicines.
- Infection of your 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 or your kneecap may become dislocated. You need to have surgery to fix this.
- Damage to nerves or blood vessels – this isn’t very common but may need further treatment.
- Stiffening due to scar tissue – the stiffness may carry on or get worse after surgery, as scar tissue builds up and restricts your movement. This can usually be treated with physiotherapy but it’s possible you may need more surgery.
Sepsis (adults)
Sepsis is a life-threatening complication that can develop if you get an infection. Sepsis is a medical emergency. Call 999 or go to A&E immediately if you have any of the following symptoms.
- Slurred speech, confusion, difficulty making sense.
- Extreme shivering or muscle pain.
- Passing no pee (urine) during a day.
- Severe difficulty breathing, feeling breathless, or breathing very fast.
- It feels like you’re going to die.
- Skin changes such as your skin looking blue, pale or blotchy, or a rash that does not fade when you roll a glass over it.
Alternatives to knee replacement surgery
Your surgeon will usually only recommend you have a knee replacement if other treatments no longer help to ease your symptoms. This includes things like physiotherapy and exercise, medicines, or using physical aids such as a walking stick. If you’re overweight, your doctor will encourage you to lose weight as this will reduce the strain on your knee. Corticosteroid injections can ease your symptoms for a few months, but this isn’t a long-term solution.
Alternative operations include the following.
- Arthroscopy (if your arthritis isn’t too bad and your knee keeps locking into place) – this is keyhole surgery where your surgeon clears out bits of debris or trims torn cartilage inside your knee.
- Microfracture – using keyhole surgery, your surgeon will make small holes in the surface layer of your bone to encourage new cartilage to grow.
Your surgeon will explain your options to you.
A knee replacement can last for up to 25 years but most last 15–20 years. Total knee replacements tend to last longer than partial knee replacements. How long they last can depend on things like how active you are and your weight, which can affect the stress on your knee joint.
See our about knee replacement surgery section for more information.
It’s best not to do any high-impact exercises, heavy lifting, or contact sports, which can weaken your new knee joint. These include sports such as tennis, running, squash, and skiing. If you want to continue doing these sports, talk to your surgeon for advice. Swimming is fine but don’t do breast stroke for the first three months as this puts pressure on your knees.
See our recovery for knee replacement surgery section for more information.
Aim to be as fit and healthy as possible before your operation to help to speed up your recovery. If you smoke, try to stop, because it will help you to recover from the operation more quickly. Prepare your home too; for example, rearrange your furniture to make it easier to move around when you get home.
See our preparation for a knee replacement and recovery for knee replacement surgery sections for more information.
You’ll usually need to wait at least 12 weeks after knee replacement surgery until you can fly. And it’s important to wear flight socks. If you’re planning to travel, ask your surgeon to find out what’s right for you.
See our recovery for knee replacement surgery section for more information.
There are over 150 different knee implants available. The most common designs are made from metal and plastic (polyethylene).
See our about knee replacement surgery section for more information.
It usually takes around 6 to 12 weeks for early recovery from a knee replacement. An essential part of your recovery will be physiotherapy. Gentle and regular exercise will help to prevent problems, such as a stiff knee. Try to build up your daily activities gradually while you heal.
See our recovery for knee replacement surgery section for more information.
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