Animation of a total knee replacement

1–2hours Typical time in theatre
1–4days Usual stay in hospital
6weeks Before driving again (3 after a partial replacement)
25years Roughly how long a new knee lasts

01About the operation

The knee is a hinge joint where the lower end of the thigh bone meets the top of the shin bone, with the kneecap at the front. The ends of the bones are covered in cartilage, which normally lets the joint move smoothly. When the cartilage is worn away by osteoarthritis or damaged by an injury, the bones rub together and the knee becomes painful and stiff.

A knee replacement may be recommended when knee pain is having a big effect on your life and other treatments haven’t worked. Most people who have one have osteoarthritis. Less often it’s done for other types of arthritis, such as rheumatoid arthritis or arthritis that develops after an injury.

Depending on the damage, the whole joint can be replaced (a total knee replacement) or just one side of it (a partial knee replacement). The operation is done in hospital, and full recovery can take several months or longer. A new knee can be expected to last around 25 years.

02Treatments to try first

Non-surgical treatment usually comes first. Your doctor may suggest:

losing weight, if you’re overweight, to ease the strain on your knee
regular low-impact exercise, such as walking, cycling or swimming, and exercises to strengthen the muscles around the knee; a physiotherapist can help with these
a walking aid
supportive footwear or shoe insoles
painkilling tablets, gels or creams
a steroid injection into the joint to ease pain and swelling

If these stop helping, the next step may be an operation to repair or strengthen the knee, or a knee replacement.

Other operations

Depending on your knee, there may be alternatives to a replacement. They aren’t suitable for everyone:

Arthroscopy: Keyhole surgery in which the joint is washed out to remove loose fragments of bone and cartilage.
Osteotomy: The angle of the shin bone is adjusted so that less weight passes through the damaged part of the knee.
Microfracture: Tiny holes are made in the surface of the bone to encourage new cartilage to grow.
Scaffold insertion: A patch or gel is placed in the knee to support the growth of new cartilage.

03Getting ready for surgery

Waiting lists can be long, so use the time to get as fit as you can: it will help your recovery. Your doctor may advise you on:

exercises to do before and after the operation
stopping smoking
eating a healthy diet
managing your weight

The pre-admission check

You may be asked to attend a pre-admission clinic a few weeks beforehand, to check you’re well enough for surgery. This can include a blood test and a blood pressure check, and it’s a chance to meet the team and ask questions.

Getting your home ready

Arrange help with everyday tasks.
Keep the things you use most within easy reach.
Stock the freezer with meals.
Organise lifts: you won’t be able to drive for several weeks.
Talk to your employer about time off and a plan for going back.

04The operation

You’ll usually be admitted on the day of surgery. The operation is done under either a general anaesthetic, so you’re asleep, or a spinal anaesthetic, which numbs you from the waist down while you stay awake.

It generally takes one to two hours. The type of operation depends on how damaged the knee is, your age and your general health.

Step by step

An incision is made down the front of the knee, and the kneecap is moved aside to reach the joint behind it.
The damaged ends of the thigh bone and shin bone are trimmed away.
New metal and plastic parts are fitted to the ends of both bones to form the new joint. Sometimes the underside of the kneecap is replaced as well.
The kneecap is returned to its place.
The wound is closed with stitches or clips and dressed.

You’ll then be looked after in the recovery area until you’re fully awake, with pain relief as you need it.

Types of knee replacement

Total knee replacement: The joint surfaces of both the thigh bone and the shin bone are replaced. This is the most common type.
Partial knee replacement: If arthritis affects only one side of the knee, just that side is replaced. The incision is smaller and recovery is usually quicker.

The National Joint Registry

After the operation you’ll be asked whether details of you and your new joint can be added to the National Joint Registry (NJR). The registry monitors joint replacements to improve patient safety and results. You can see Mr Syed’s NJR surgeon profile (opens in a new tab).

05Recovery

Full recovery can take several months or longer, depending on your age and general health, and is usually quicker after a partial replacement. Following the hospital’s advice will help you get the best result.

In hospital

Your knee will be sore, and you’ll have painkillers for the first few days. Nurses and physiotherapists will get you up and walking soon after the operation, with crutches or a frame to begin with.

Going home

Most people go home one to four days after surgery, once there are no signs of complications and they can get about safely on crutches. You’ll usually be given compression stockings to wear to help prevent blood clots. A physiotherapist or occupational therapist will show you how to manage at home and give you exercises; doing them from the start helps the knee regain strength and movement.

Stitches or clips usually come out after about 10 days, and you’ll have a follow-up appointment around six weeks after the operation.

Use crutches or sticks at first, cutting down to one crutch and then a stick as your confidence grows.
Try walking without an aid after about six weeks, if you feel ready.
Wear your compression stockings day and night, taking them off only to wash them. Most people need them for at least six weeks.
Wait at least six weeks before driving after a total knee replacement, or three weeks after a partial one, and check with your doctor first.
Keep your leg raised when you can, to reduce swelling.
Keep up the exercises your physiotherapist gives you.
Go back to work when you feel ready, usually after six to twelve weeks depending on your job.

Avoid

Crossing your legs for the first six weeks.
Twisting the knee, bending down or reaching up more than you have to.
Sleeping with a pillow under the knee. You don’t need a special sleeping position.
Kneeling on the new knee until your doctor says it’s fine.
Standing for long periods, which can make your ankles swell.
Heavy household jobs, such as vacuuming or carrying shopping, for the first three months.

06Risks and complications

Most people have no complications after a knee replacement, and those that do happen are usually minor and treatable. Your risk depends on your age and general health, and your surgeon will explain it before you agree to the operation.

Blood clots: A clot in a leg vein (DVT) is possible after surgery and is often not serious. Occasionally a clot travels to the lungs (a pulmonary embolism), which is serious. Compression stockings or blood-thinning medicine help prevent clots, and blood thinners are also used to treat them.
Infection: There’s a small risk of the wound becoming infected. This is usually treated with antibiotics; an infection deep in the joint may need further surgery.
Damage to nerves or tissue: A nearby nerve, blood vessel or ligament can be damaged during surgery. This is uncommon, and can usually be repaired at the time or heals afterwards.
Ongoing problems with the knee: Some people have lasting pain or stiffness, find it hard to bend the knee, or feel it give way when they stand or walk. Physiotherapy and exercises can help.
Wear over time: Because a new knee lasts around 25 years, some people need a second (revision) operation later in life, though this isn’t common.

Get urgent advice

Ask for an urgent GP appointment or contact NHS 111 (opens in a new tab) if you’ve recently had a knee replacement and you have:

throbbing or cramping pain in your leg
a high temperature, or you feel hot, cold or shivery
pus or other discharge from the wound
redness, tenderness, swelling or pain in your knee that isn’t improving or is getting worse

These can be signs of an infection or a blood clot.

Call 999 or go to A&E

if you have pain and swelling in your leg and:

you’re finding it hard to breathe
you have chest pain

This could be a clot in the lungs (pulmonary embolism), which needs treatment straight away. Don’t drive yourself: ask someone to take you or call 999 for an ambulance, and bring any medicines you take.

Total Knee Replacement