Knee Replacement

Overview

A knee replacement (also called knee arthroplasty) is an operation to replace the worn or damaged surfaces of your knee joint with smooth, man-made parts. Your knee is a hinge joint where the thigh bone meets the shin bone, with a small bone called the kneecap in front. When the cartilage (the slippery cushion that covers the ends of these bones) wears away, the bones rub together and the knee becomes painful and stiff. During surgery, the surgeon removes the damaged surfaces and fits a metal and plastic joint in their place. This usually eases pain and helps you move more easily. The operation is done by an orthopaedic surgeon (a doctor who specialises in bones and joints), often under a spinal or general anaesthetic.

Yes, it is very common. Every year, hundreds of thousands of knee replacements are carried out around the world. It is one of the most frequently performed planned operations in the UK and many other countries, and the numbers have been rising as people live longer and stay active for longer.

Knee replacement is most often done for people in their 60s, 70s and 80s whose knee pain has become severe. It can also be done for younger people whose knee has been badly damaged by injury or another joint condition. It is slightly more common in women than in men. Your weight, your level of physical activity, and whether you have had a knee injury before can all affect your chance of needing one.

Symptoms

Common symptoms

• Knee pain that gets worse over months or years, especially when you walk, climb stairs or stand up from a chair
• Stiffness, particularly first thing in the morning or after sitting for a while
• Swelling in and around the knee
• A grinding, crunching or clicking feeling when you move the knee
• Pain that keeps you awake at night or aches even when you are resting
• The knee feeling weak or giving way
• Difficulty kneeling, bending down or getting in and out of a car
• Needing to use a stick or hold on to furniture to get around

Causes

Main causes

• Osteoarthritis: the most common cause. The cartilage cushion wears thin over time and bones rub together.
• Rheumatoid arthritis and other inflammatory joint diseases, which can damage the joint surface.
• Previous knee injury, such as a broken bone, torn ligament or torn cartilage, which can lead to early wear and tear.
• Long-standing joint problems present from birth or childhood that affect how the knee lines up.
• Less commonly, conditions where the bone itself is damaged, such as a loss of blood supply to part of the bone.

Risk factors

• Increasing age
• Being overweight or living with obesity, which adds load to the knees
• A past knee injury or knee surgery
• Heavy manual work, kneeling, or climbing many stairs day to day
• Family history of osteoarthritis
• Weak thigh muscles and low levels of physical activity
• Participating in high-impact sports over many years

When to see a doctor

See a doctor urgently if:

• A knee that is hot, very red, very swollen and painful, especially with a fever
• A knee that locks, or that you cannot straighten or bend at all
• Sudden severe swelling after an injury, or being unable to put weight on the leg
• New calf pain or swelling, or sudden breathlessness after any knee surgery

Book a routine appointment if:

• Knee pain that has lasted more than a few weeks and is not improving
• Pain that is limiting your walking, work, sleep, or everyday activities
• Stiffness that makes it hard to bend the knee or get up from a chair
• If you and your doctor are considering whether surgery is right for you

Diagnosis

A doctor will usually start by asking about your pain, how it affects your daily life, and your medical history. They will examine your knee, checking how far it bends and straightens, whether it is swollen or tender, and how stable it feels. Based on this they may arrange an X-ray, and sometimes other tests. Being referred to a specialist knee doctor or an orthopaedic team is common if surgery is being considered.

Tests that may be done

• X-ray of the knee, which shows how much the joint space has narrowed and whether there are bone spurs
• Blood tests, sometimes used to look for inflammation or infection
• Magnetic resonance imaging (MRI) or a computerised scan (CT), used less often if other problems are suspected
• Removing and testing a small sample of fluid from the knee if infection or gout is possible

What to expect at your appointment

You may have your knee examined and be asked to walk a short distance so the doctor can see how you move. Appointments to discuss surgery usually involve a shared decision: you, your family or carers, and the surgical team will look at your X-rays and talk about the benefits and risks. You may be asked about your home, who can help you, and what you hope to get back to doing. There is no pressure to decide straight away, and it is fine to ask for more time or a second opinion.

Treatment

Treatment starts with simpler options and only moves on to surgery if pain is still badly affecting your life. Many people get good relief from exercise, physiotherapy, weight management and pain relief. Your doctor will help you find the combination that suits you.

Self-care at home

• Stay active. Gentle, regular movement keeps the joint and muscles working better than rest.
• Try low-impact activities such as swimming, cycling and walking short distances regularly.
• Build the muscles around your knee with exercises from a physiotherapist (a movement and exercise specialist).
• If you are overweight, losing even a modest amount of weight can take real pressure off your knees.
• Use a walking stick, trekking poles or grab rails if they help, and pace yourself with rest between activities.
• Apply a warm pack or cold pack for short periods, whichever feels soothing, wrapped in a cloth.
• Wear supportive, well-cushioned footwear.
• Keep a simple diary of what makes the pain better or worse, which helps at appointments.

Medical treatments

Doctors treat knee arthritis with a range of approaches rather than one single cure. These include pain-relieving medicines that you and your doctor choose together, creams or gels rubbed into the knee, physiotherapy and structured exercise programmes, walking aids, and sometimes injections into the joint to reduce pain for a while. Your doctor or pharmacist can explain the benefits and risks of any option, including the possible side effects. Steroid tablets are sometimes used in inflammatory conditions. It is important to keep reviewed: what works for one person may not work for another, and medicines should be checked regularly rather than continued indefinitely.

When is surgery considered?

Surgery is usually considered when knee pain is severe and long-lasting, other treatments have been tried, and daily life, sleep or mood are seriously affected. Your surgical team will also weigh up your general health, your weight, whether you smoke, and how likely you are to benefit. Knee replacement is a big operation with a long recovery, so the decision is made together with you. Some people are offered partial (half) knee replacement, or another type of operation, depending on which part of the knee is damaged.

Living with this condition

Right after surgery you will be encouraged to get up and move quite quickly, with support. You will use crutches or a frame for a few weeks and will need help at home for a while. Most people find the first two to six weeks the hardest, with swelling and tiredness. Gradually walking, stairs and daily tasks get easier. Many people are back to most everyday activities within three months, and the knee keeps improving for up to a year. You may hear or feel a clunk in the new joint; this is common and usually harmless, but mention it at a check-up if it worries you.

Lifestyle tips

• Do your exercises every day, even when you feel better. They are what keeps the new knee working well.
• Build walking up gradually, starting on flat, even ground.
• Avoid high-impact activities such as running and jumping, and ask your team about sports you enjoy.
• Use a small cushion to raise your foot when sitting, and avoid kneeling on the scar until you are told it is safe.
• Take care of the scar: keep it clean and dry as advised, and protect it from sun.
• Plan rest breaks into your day, especially in the first few months.
• Keep to check-ups and tell your team about any new pain, swelling or stiffness.

Diet and exercise

There is no special diet that makes a new knee heal faster, but eating well helps recovery. Aim for regular meals with plenty of vegetables, fruit, beans and pulses, whole grains, and a source of protein at each meal (such as eggs, fish, chicken, dairy, tofu or lentils) to help rebuild muscle. Drink enough water. Gentle exercise is central: walking, cycling on an exercise bike, swimming and the specific strength and movement exercises given by your physiotherapist. A physiotherapist can tailor a plan to you. Ask your doctor or pharmacist if you are unsure about supplements.

Mental health and emotional wellbeing

It is very common to feel anxious before surgery and frustrated or low during recovery. Progress is not always a straight line, and some days will be harder than others. Feeling tired, dependent on others, or worried about getting back to work or hobbies is normal. If low mood, worry or poor sleep lasts more than a couple of weeks or starts to affect your daily life, please tell your doctor or surgical team. They can offer support, and there is no shame in asking. If you ever feel you cannot cope or have thoughts of harming yourself, contact your local crisis service or emergency number straight away.

Prevention

Not all knee replacements can be prevented, especially where arthritis runs in the family or a joint has been badly injured. But you can lower your risk and protect your knees: keep your weight in a healthy range, stay physically active with low-impact exercise, keep the muscles around your knees strong, warm up before sport, and treat knee injuries properly. If you already have knee pain, getting help early from a physiotherapist can make a real difference.

Screening programmes

There is no routine screening test for the arthritis that leads to knee replacement. If you have ongoing knee pain, stiffness or swelling, see your doctor rather than waiting for a check-up.

Complications

If left untreated

• Pain that slowly worsens and starts to limit walking, work and sleep
• Increasing stiffness, so the knee bends or straightens less
• Muscle weakness in the thigh and calf from using the leg less
• Weight gain and lower fitness from reduced activity
• Greater risk of falls, especially in older adults
• Low mood, isolation and loss of independence as activities are given up
• In some people, the knee becoming increasingly bowed or bent over time

Long-term outlook

The outlook is generally very good. Most people who have a knee replacement get much less pain and can walk further and do more of what they enjoy. Recovery takes patience, and it is normal to have good days and harder days. The new joint is not the same as a natural knee: it may not bend quite as far, and you will usually be advised to avoid running and high-impact sport. Most knee replacements last many years, though some eventually wear out and need further surgery. Whatever you decide, you do not have to face it alone. Your GP, physiotherapist and surgical team are there to help you make the choice that is right for you, and to support you afterwards. Please talk to a qualified healthcare professional about your own situation.

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