Knee Replacement Surgery

Overview

Knee replacement surgery (doctors also call it knee arthroplasty) is an operation to replace the worn or damaged surfaces of your knee joint with an artificial joint. The artificial joint — often called an implant or prosthesis — is usually made of metal and strong plastic. It is shaped to work like your own knee, letting it bend and straighten. The operation is done to ease pain that has not improved with other treatment and to help you walk and move more easily.

Yes. Knee replacement is one of the most commonly performed operations worldwide, and many thousands are done every year. Because it is so common, surgeons and hospitals have well-tested routines for preparing people and helping them recover.

It is most often done for people in their 60s, 70s and 80s whose knee has been worn down by arthritis. It can also be done for younger people whose knee is badly damaged by injury, arthritis or other joint problems. Body weight, previous knee injuries, heavy physical work and family history all play a part in who develops severe knee arthritis.

Symptoms

Common symptoms

• Knee pain that is worse when you walk, climb stairs, kneel or stand up from a chair
• Stiffness, especially in the morning or after sitting for a while
• Swelling in and around the knee
• A grinding, crunching or clicking feeling in the knee
• The knee giving way or feeling unstable
• Not being able to bend or straighten the knee fully
• Pain at rest or at night in more advanced cases
• Weak muscles around the thigh, making the leg feel less reliable

Symptoms in children

• Knee replacement is very rarely done in children or teenagers, and only for serious joint disease or after major injury, decided by specialist teams
• Knee pain in a child is usually caused by something else — such as growth-related pain, injury, or inflammation — and should always be checked by a doctor
• A child with a hot, swollen, painful knee, or who cannot bear weight, needs to be seen urgently

Symptoms in older adults

• Pain that limits walking distance and makes shopping, housework or gardening hard
• Difficulty getting out of a low chair, or fear of falling on stairs
• Muscle weakness and poorer balance, which can raise the risk of falls
• Pain that disturbs sleep and lowers mood or energy
• Stiffness after sitting, which eases after a few steps

Causes

Main causes

• Osteoarthritis — the smooth cartilage lining the knee wears away, so bone rubs on bone
• Rheumatoid arthritis and other inflammatory joint conditions that damage the joint lining
• Arthritis that develops years after a knee injury, such as a torn ligament or a broken bone near the knee
• Long-term wear from very physically demanding work or high-impact sport
• Less common causes, such as poor blood supply to the bone, joint infection in the past, or joint problems present from birth

Risk factors

• Getting older
• Carrying extra body weight, which puts more load on the knees
• A previous knee injury or knee operation
• A job or sport that involves a lot of kneeling, lifting, squatting or impact
• Family history of knee arthritis
• Weak thigh and hip muscles
• Arthritis in other joints, or a condition such as rheumatoid arthritis

When to see a doctor

See a doctor urgently if:

• A hot, very swollen, extremely painful knee, especially with a fever
• Chest pain, sudden breathlessness, or coughing up blood — call your local emergency number right away
• Calf pain and swelling, or new numbness or weakness in the leg
• A wound that is leaking pus or opening after surgery
• A knee that gives way and cannot bear weight

Book a routine appointment if:

• Knee pain that has lasted more than a few weeks or keeps coming back
• Pain that is limiting your walking, work, sleep or enjoyment of life
• Stiffness that makes everyday tasks such as getting dressed or using stairs difficult
• Knee pain that is not settling with rest, activity changes and simple pain relief
• You want to talk about whether surgery might be an option for you

Diagnosis

There is no single test that decides whether you need a knee replacement. Your doctor will talk with you about your pain, how far you can walk, what your knee can and cannot do, and how much it affects your life. They will examine your knee, look at how you walk, check how far it bends and straightens, and check the strength of the muscles around it. Imaging and tests help show how much damage there is, but the decision is based on your symptoms and your goals as much as on the pictures.

Tests that may be done

• A physical examination of the knee, hips and walking pattern
• X-rays, usually taken standing up, to show joint space and bone changes
• Sometimes an MRI scan or CT scan for more detail
• Blood tests if an inflammatory condition or infection is suspected
• Sometimes a small sample of joint fluid is taken to rule out infection or gout
• Pre-operative checks once surgery is planned, such as blood tests, heart tracing and a review of other health conditions

What to expect at your appointment

You may be referred to an orthopaedic team (bone and joint specialists). Appointments often include a review of your X-rays, a discussion of the risks and benefits, and a chance to ask questions. In many services you will also be offered a class or session to prepare you for surgery, including exercises to start beforehand and practical plans for home, work and driving. It is fine to take your time and to ask about alternatives before deciding.

Treatment

Treatment usually starts with steps that do not involve surgery and moves on only if these stop helping enough. The aim is always to reduce pain, keep you moving and protect the joint. Options include physiotherapy-led exercise, weight management where relevant, activity changes, walking aids, pain-relieving medicines, and sometimes injections into the knee. Surgery is considered when pain and stiffness seriously affect your quality of life despite these approaches.

Self-care at home

• Keep moving: short, regular walks and daily knee and thigh exercises are better than long bursts of activity followed by rest
• Build up the muscles around the knee and hip — stronger muscles support the joint and reduce pain
• Use a walking stick or poles if they help you walk further with less pain
• Change how you do things: sit on higher chairs, use a trolley in the kitchen, take the stairs one at a time
• Apply a cold pack wrapped in a cloth for 15 to 20 minutes to a swollen knee
• Try to keep to a healthy weight if you can — even modest weight loss reduces load on the knees
• Choose low-impact activity such as walking, swimming, cycling or using an exercise bike
• Pace yourself and plan rest breaks on busy days
• Wear supportive, well-cushioned shoes
• Stop smoking if you smoke — it helps healing, including if you have surgery

Medical treatments

Doctors can offer pain-relieving medicines taken by mouth or rubbed on the skin, given at the lowest dose that helps. Injections into the knee can sometimes ease pain for a while, but the relief is usually temporary. Physiotherapy is a core treatment — a physiotherapist can teach you specific exercises and ways to move that protect the joint. Walking aids and, in some cases, braces or foot insoles may help. Your doctor or pharmacist can talk through the risks and benefits of each option so you can choose what suits you. Always check with a pharmacist or doctor before starting or combining medicines, especially if you have other health conditions.

When is surgery considered?

A knee replacement is usually considered when knee pain and stiffness are severe, have not improved enough with other treatment over time, and are having a real impact on your sleep, mood, work or everyday activities. Your doctor or specialist team will discuss the benefits and risks with you, including the recovery time and the small chance of problems. The decision is yours as well as theirs — it is reasonable to ask for time to think, or to get a second opinion.

Living with this condition

Most people stay in hospital for a few days after surgery. In the first two weeks you will need help at home, use crutches or a frame, and rest with your leg raised. You will be given exercises to do several times a day, and a physiotherapist will guide you. Walking short distances usually feels easier by around 6 weeks, driving is often possible again after about 6 to 8 weeks if you can control the car safely and your surgeon agrees, and many people return to lighter work at around 6 to 12 weeks. Full recovery, including strength and stamina, often takes up to a year. Expect some swelling and stiffness for several months — this is normal and usually improves gradually.

Lifestyle tips

• Do your physiotherapy exercises even on days when you feel better — consistency matters more than effort
• Build walking distance gradually, and use a stick or poles if you feel unsteady
• Prepare your home before surgery: remove loose rugs, keep often-used items within reach, and arrange a firm chair with arms
• Arrange help with shopping, cooking and pets for the first few weeks
• Follow your surgical team's advice about wound care, bathing and when to restart activities
• Avoid kneeling on the new knee for a while, and ask your team when it is safe
• Return to low-impact exercise such as swimming, cycling and walking once cleared, and be cautious with high-impact sport
• Pace yourself and build rest into busy days

Diet and exercise

Eat regular balanced meals with enough protein to help healing — for example beans, lentils, eggs, fish, chicken, dairy or tofu — along with fruit, vegetables and wholegrains. If you are carrying extra weight, gentle, steady weight loss reduces strain on the new joint and on your other knee. Keep hydrated. Exercise is the most important long-term habit: aim for a mix of daily walking, strengthening exercises for the thigh and hip, and gentle stretching. A physiotherapist can give you a safe plan that matches your stage of recovery. If you have other conditions such as diabetes or heart disease, ask your team how to adapt your routine.

Mental health and emotional wellbeing

It is very common to feel anxious before surgery and frustrated during recovery. Progress can feel slow, sleep can be disrupted, and needing help from others can be hard. Many people also feel low in the first few weeks. These feelings usually ease as pain settles and movement improves. Tell your doctor, nurse or physiotherapist if low mood, worry or poor sleep is building up — there is good support available, and it is not a sign of weakness. If you ever feel you cannot cope or have thoughts of harming yourself, contact your local crisis service or your local emergency number straight away, and reach out to someone you trust.

Prevention

You cannot fully prevent the arthritis that leads to knee replacement, but you can lower your risk and protect your knees. Staying active, keeping muscles strong, avoiding knee injuries, warming up before sport, and keeping to a healthy weight all help. If you already have knee arthritis, good exercise habits, physiotherapy and weight management can reduce pain and may delay or avoid the need for surgery. Preventing falls and keeping bones strong also matters as you get older.

Vaccines

There is no vaccine that prevents knee arthritis or the need for a knee replacement. Keeping up with routine vaccinations is still worthwhile, and your doctor may advise extra ones before surgery — for example, some teams recommend a tetanus check or flu vaccination. Ask your GP or pharmacist what is recommended for you.

Screening programmes

There is no national screening programme for knee arthritis. If you have ongoing knee pain, stiffness or swelling, see your doctor for an assessment rather than waiting for a screening test.

Complications

If left untreated

• Pain and stiffness that slowly get worse, making walking, stairs and getting up from a chair harder
• Muscle weakness and poorer balance, which increase the risk of falls
• Becoming less active, which can affect weight, heart health and mood
• Poor sleep and low mood from continuing pain
• Changes in the shape of the leg, and strain on the other knee, hip or back
• Loss of independence in daily tasks

Long-term outlook

Most people who have a knee replacement get a lot of relief from pain and can walk and manage daily life more easily. Many implants last 15 to 20 years or more, and some last longer. Recovery takes time and effort, and it is normal to have good days and harder days. As with any operation there are risks, such as infection, blood clots, stiffness, or the implant loosening over time — your surgical team will explain these and how they are reduced. If you are considering surgery, the most useful next step is an honest conversation with your doctor or specialist team about your goals, your general health and what recovery would look like for you.

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