Knee replacement

A knee replacement is a common operation to remove worn or damaged parts of your knee joint and replace them with an artificial joint, to help you move more easily and to reduce pain.

There are two main types of knee replacement — partial knee replacement and full knee replacement.

Knee pain is often caused by wear or damage, usually as a result of osteoarthritis but can also be caused by trauma or other conditions that damage the knee joint, such as:

• Avascular necrosis – death of the knee joint due to a lack of blood supply
• Bone dysplasia (unusual bone growth)
• Gout
• Haemophilia
• Knee deformity or injury
• Rheumatoid arthritis

Who needs knee replacement surgery?

You may need a knee replacement at any age, however, getting older increases your risk — those aged between 60 and 80 are most likely to need a knee replacement. Genetics, previous knee injury and lifestyle can also play a part in whether you need a knee replacement, so always seek medical advice if you have symptoms.

Your doctor may recommend knee replacement if:

• You find it difficult carrying out everyday tasks
• You have depression due to pain or reduced mobility
• Your mobility is reduced
• Your quality of life is impacted, including your sleeping
• You’re unable to work or socialise

Knee replacement surgery can relieve pain and help you become more active again. However, you must be healthy enough to undergo surgery.

Alternative treatments to knee replacement

Your doctor may suggest an alternative to knee replacement, although the results may not last as long. These treatments are often performed using arthroscopy — a type of keyhole surgery using a thin, flexible, telescopic instrument called an arthroscope.

Knee replacement alternatives include:

• Arthroscopic washout – flushing the knee joint with fluid using keyhole surgery, often performed with debridement (removal of loose bone or cartilage); this is less common than it used to be
• Ligament surgery to reconstruct damaged ligaments
• Microfracture – your surgeon makes small holes in your bones to stimulate cartilage growth
• Mosaicplasty – transferring healthy cartilage taken from the edge of your joint to the damaged area
• Osteotomy – the shin bone is cut and realigned to reduce the weight carried by the damaged part of your knee

Your doctor will usually only recommend surgery after you’ve tried other non-invasive alternatives to knee replacement without success. Other treatments include:

• Lifestyle changes
• Medications
• Physiotherapy
• Steroid injections

You’ll need to be examined by your orthopaedic surgeon. They will assess the range of movement of your knee, as well as its strength and stability.

You’ll also need an X-ray to show any wear or damage to your joint. Our fast diagnostics means you won’t have to wait long to find out whether knee replacement surgery is right for you. Your consultant will discuss what would be best for you and your lifestyle, so it’s a good time to talk about what you want. They will consider your:

• Activity level
• Age
• Knee size and shape
• Overall health
• Weight

As well as the potential benefits of reducing pain, increasing mobility and improving your quality of life, there are disadvantages of knee replacement surgery to consider:

• As with all major surgery, there are some risks of complications
• You’ll be less mobile for the first few weeks after the operation so you may need some help around the house and with errands
• Your new knee joint may eventually need revision surgery after about 20 years
• Your new joint won't be able to bend as far as a natural knee

Your consultant will take you through both the advantages and disadvantages of knee replacement surgery so you can make an informed decision.

In a healthy knee joint

Your knee is a hinge joint formed where your thigh bone meets the shinbone of your lower leg. The ends of your bones and kneecap are covered in smooth cartilage — tissue that helps your bones glide easily across each other.

In an unhealthy knee joint

The cartilage is worn away, causing damage to the ends of your bones at the joint and making it painful and difficult to move.

Knee replacement surgery

Before your operation, you should try stay as active as possible and try strengthening muscles around your knee to help your recovery.

During the operation, your surgeon will position your knee in the bent position to better expose the joint. They will then make a 15-25cm incision below your knee and move your kneecap aside.

They will remove your damaged cartilage and the ends of your thigh bone and shinbone, and replace them with an artificial joint — the end of your thigh bone will be replaced with a metal shell and the end of your shinbone with a flat piece of plastic with a metal stem. Depending on the condition of your kneecap, they may also place a plastic button under the kneecap.

All of the artificial parts placed in your knee are together called the prosthesis. The prosthesis is measured to fit your joint beforehand. Once your prosthesis is in place, your surgeon will bend and rotate your knee to check it works properly.

The surgery is carried out under a general anaesthetic or a spinal or epidural anaesthetic where you’re awake but can’t feel anything below your waist.

There are two main kinds of knee replacements: total knee replacement surgery and partial knee replacement surgery.

Total knee replacement

Your surgeon will make an incision along the side of your knee to expose your kneecap and move it aside. They will remove the damaged ends of your thigh bone and shinbone and will replace both sides of your joint, and sometimes the back of your kneecap, with a precisely-measured prosthesis.

First, a dummy joint is placed so your surgeon can check that the joint works. Any adjustments are made and the bones cleaned before your final prosthesis is fitted.

Your surgeon replaces the end of your thigh bone with a curved piece of metal and your shinbone with a flat metal plate. A plastic spacer is positioned between the two metal parts to reduce friction as you bend your knee.

This prosthesis is fixed in place with cement and your wound cleaned and stitched up. Finally, a dressing is applied to protect your wound. In some cases, a splint is placed to keep your leg immobile, however, in most cases, it is recommended that you start moving your knee as soon as possible.

The procedure takes up to three hours.

Partial knee replacement

If you have less damage, your surgeon may only need to replace one side of your joint using a partial knee replacement.

Recovery will usually be faster and you may have greater improvement in your mobility and more natural movement than with a total knee replacement. One in four people with osteoarthritis is suitable for partial knee replacement.

For partial knee replacement, your surgeon may perform mini-incision surgery using smaller cuts and instruments to improve recovery time — this also reduces scarring. A blood transfusion after surgery is usually not needed. 

As well as total and partial knee replacement, there are other procedures that may be suitable.

Kneecap replacement

Also called a patellofemoral replacement or patellofemoral joint arthroplasty, this is a less complex surgery than a knee replacement if only your kneecap is damaged. This is not usually suitable if you have osteoarthritis and the long-term outcomes are not yet clear.

Bi-lateral knee replacement

Also known double knee replacement surgery, the procedure involves replacing both knees at the same time. This may be suitable if you have osteoarthritis in both of your knees as it means you only need one surgery and one period of recovery. However, this surgery usually involves a longer recovery period and more support during your recovery than a single knee replacement.

Complex or revision knee replacement

If you have major bone loss, a deformity or ligament weakness, you might need a complex or revision knee replacement. The artificial joint has a longer stem that fixes into your bones and additional components that can give you more stability. Revision knee replacement surgery is also sometimes used if you need to have a knee replacement redone.

Advances in surgery

Exciting recent advances mean that surgeons can often operate using smaller incisions, so there’s less impact on your surrounding muscles and tendons and you’ll recover more quickly — this is called mini-incision surgery. Artificial joints (prostheses) can even be created using MRI scans and 3D printing to tailor the size and shape to your knee.

Some of our hospitals also use computer-assisted (image-guided) surgery to enable the surgeon to position the replacement more precisely. Some hospitals also use pre-programmable robotic arms to help fit your joint.

Who will be involved?

As well as your chosen surgeon, your care team will include:

• A consultant radiologist — an expert in assessing images taken during scans (such as an X-ray or MRI scan)
• A physiotherapist — before and after surgery
• An anaesthetist to administer anaesthetic during the operation

A doctor is also available to see you if you have any medical issues or complications after surgery.

Preparing for your knee replacement operation

Your consultant or physiotherapist will recommend exercises you can do to strengthen the muscles around your knee before surgery to improve your recovery time.

It’s also a good idea to prepare your home for after your operation to make it easier for you to get around safely and more easily. Make sure you:

• Arrange to have crutches or a walking frame ready
• Have a stable bench or chair to use in your shower
• Have a stable chair with back support and a firm seat cushion
  • Install:
    a toilet seat raiser
  • safety handrails in your bath or shower
  • safety handrails along your stairway
• Make sure important items are easy to reach — arrange your living space so everything you need is on one floor to avoid having to climb stairs
• Remove anything you can trip over

Research what’s involved with a knee replacement surgery so you can ask your care team any questions and know what to expect on the day and during your recovery.

Before your operation, you’ll have a pre-operative assessment appointment with a nurse to check your general health before surgery and discuss any medications you’re currently taking that you may need to stop or adjust before surgery.

Most knee replacement surgery is carried out using general anaesthetic. Typically, you must not eat for about six hours or drink for two hours before general anaesthesia. 

You will be told to avoid certain fluids (milk); instead, water or black tea or black coffee is usually recommended. You’ll also need to wear compression stockings during and after surgery to avoid blood clots in your leg while you’re immobile.

How long does knee replacement surgery take?

Usually between one and three hours, depending on whether you’re having a total knee replacement or a partial knee replacement.

Anaesthetic choices

Your consultant will help you decide what anaesthetic is best for you. You'll have either a general, spinal or epidural anaesthetic, so you’ll be fully unconscious or awake but unable to feel anything from the waist down. If you have the spinal or epidural options, you may have a sedative to help you feel more relaxed.

You may also receive a nerve block around your knee to numb it.

Before, during and after your surgery, you will be given antibiotics to prevent infection.

Pain after knee replacement

Everyone experiences pain differently and you’re likely to feel discomfort for some time afterwards. But don’t worry, you’ll be given painkillers after the operation and we can help you to manage any pain in the following days and weeks.

Your hospital stay

The average hospital stay is two to five days, with total knee replacements requiring longer than partial knee replacements.

Recovery can take several months and you’ll need to do knee replacement exercises and have physiotherapy regularly to improve your mobility.

Short term side effects

Immediately after your surgery, you may need to be given oxygen and/or a blood transfusion. Your wound may need to be drained and your dressings will need to be changed regularly. You will likely feel very tired.

You will have some pain in your knee after the operation so you’ll be given painkillers and you can continue to take over-the-counter painkillers when you’re home. You will need to use crutches or a walking frame at first.

Your knee, legs and feet may be swollen — you can try keeping your leg raised or using an ice pack in a tea towel for 20 minutes every three to four hours to help. Your care team will encourage you to move your foot and ankle to improve the blood flow to your leg muscles and help reduce swelling and prevent blood clots. They will also recommend breathing exercises and gradually increasing your activity level.

You’ll need someone to take you home after your operation and to help with errands around the house for the first few days as you regain some mobility. The stitches in your knee will need to be removed around 10-12 days after your operation or they’ll gradually disappear if they’re dissolvable stitches.

Physiotherapy and ongoing treatment

Soon after surgery, our physiotherapist will take you through a series of exercises designed to strengthen the muscles around your new knee and improve and optimise movement of the joint. It’s important you carry on doing them after you’ve left hospital. This will help speed up your recovery so you can enjoy normal activities again.

You will need to use a walking aid for around six weeks after your surgery.

Your lifestyle after treatment

Many people enjoy a full and active life after knee replacement surgery. You can take part in most low-impact sports, although your consultant will tell you if you need to wear a leg brace.

Our team will support you all the way to get the most from your surgery.

Looking after your new knee

You will need to use crutches or a walking frame after your knee replacement surgery but should gradually reduce the amount you need to use them.

Continue with the exercises prescribed by your physiotherapist to prevent stiffness but don’t force your knee into positions if it is not comfortable.

Make sure you wear supportive shoes when you are outside.

What not to do after a knee replacement

Make sure you do not:

• Kneel on your knee until your surgeon advises that you can
• Sit cross-legged for at least six weeks after your surgery
• Sleep with a pillow under your knee as this can cause a permanently bent knee
• Twist your knee

How long does a knee replacement last?

Most knee joint replacements last for 20 years or more. However, in one in 20 cases, further surgery will be needed in around 12 years.

Your prosthetic knee joint can wear out, particularly if you perform high-impact activities or are overweight.

Most people have knee replacement surgery without complications, but all surgery carries risks and your consultant will explain them to you before you go ahead.

Pain after knee replacement is a common short-term side effect — pain at night is particularly common. Swelling and weakness often also occur in the short term.

You’ll have some scarring, which will gradually fade with time.

Knee replacement surgery complications

Complications can include:

• A blood clot — this can occur in your:
  • Leg — this is called deep vein thrombosis (DVT); symptoms include hard, hot, red or painful areas in your leg 
  • Lungs — this is called a pulmonary embolism (PE); it is rare but is a medical emergency; symptoms include chest pains and breathlessness
• A dislocated kneecap — in most cases, this can be repaired with surgery
• Abnormal bone growth — this may limit the movement of your knee and need further surgery to restore movement
• Excess scar tissue
• Failure of the artificial knee joint — this includes: 
  • Fracture — this may occur during or after surgery
  • Infection of the knee joint — this is usually treated with antibiotics and further surgery
  • Instability — this may need further surgery
  • Joint stiffness 
• Limited relief of pain or persistent knee pain

Other complications include:

• Blood vessel, ligament and/or nerve damage around your knee joint
• Numbness around the site of surgery
• Unexpected bleeding into your knee joint

Signs of serious complications

• Chest pain or breathlessness — these are signs of a PE (a blood clot in your lungs) and is a medical emergency
• Hard, hot, red or painful areas in your leg — these are signs of DVT (a blood clot in your leg)

Signs of infection after a knee replacement

• Chills
• Fever
• Fluid leaking from your wound
• Increasing pain, redness, swelling and tenderness in and around your knee

If your knee joint is infected, you will usually need antibiotics and further surgery to remove your prosthetic knee. After the infection has gone away, you will need to have another knee replacement surgery to install a new prosthetic knee.

Risks of general anaesthetic

Serious complications associated with general anaesthetic do occur, but they're extremely rare.

For most people, the benefits in terms of controlled unconsciousness and removal of pain are much greater than the disadvantages.

It’s estimated that serious complications result in approximately four deaths for every million anaesthetics given. The pre-operative assessment is carried out to limit the risk of any complications occurring.

Your risk of complications due to general anaesthetic increase with age and if you have underlying health conditions that affect your heart or lungs.

At Spire Healthcare hospitals, your safety is our top priority. We have high standards of quality control, equipment and cleanliness and an ongoing system of review and training for our medical teams.