You'll usually be admitted to hospital on the day of your operation. The surgeon and anaesthetist will usually come and see you to discuss what will happen and answer any questions you have.

Most people would have seen their surgeon at a pre-assessment clinic and had the chance to the operation.

A senior-level surgeon, consultant or registrar will do the operation. They may be helped by junior doctors. You should be told at your pre-operative assessment who will be doing the operation. Ask if you're not told.

How the operation is done

Knee replacement surgery is usually performed either under general anaesthetic (you're asleep throughout the procedure) or under spinal anaesthetic or epidural (you're awake but have no feeling from the waist down).

The worn ends of the bones in your knee joint are removed and replaced with metal and plastic parts (a prosthesis) which have been measured to fit.

You may have either a total or a partial knee replacement. This will depend on how damaged your knee is. Total knee replacements are the most common.

Read more information about what happens on the day of your operation.

Total knee replacement

In a total knee replacement, both sides of your knee joint are replaced. The procedure takes 1 to 3 hours:

• Your surgeon makes a cut down the front of your knee to expose your kneecap. This is then moved to the side so the surgeon can get to the knee joint behind it.
• The damaged ends of your thigh bone and shin bone are cut away. The ends are precisely measured and shaped to fit the prosthetic replacement. A dummy joint is positioned to test that the joint is working properly. Adjustments are made, the bone ends are cleaned, and the final prosthesis is fitted.
• The end of your thigh bone is replaced by a curved piece of metal, and the end of your shin bone is replaced by a flat metal plate. These are fixed using special bone 'cement', or are treated to encourage your bone to fuse with the replacement parts. A plastic spacer is placed between the pieces of metal. This acts like cartilage, reducing friction as your joint moves.
• The back of the knee cap may also be replaced, depending on the reasons for replacement.
• The wound is closed with either stitches or clips and a dressing is applied to the wound. In rare cases a splint is used to keep your leg immobile, but you're usually encouraged to move your knee as early as possible.

You're likely to still have some difficulty moving after your operation, especially bending your knee. Kneeling may be difficult because of the scar.

Partial (half) knee replacement

If only one side of your knee is damaged, you may be able to have a partial knee replacement. This is a simpler operation, which involves a smaller cut and less bone being removed. It's suitable for around 1 in 4 people with osteoarthritis.

The advantages of partial knee replacement include a shorter hospital stay and recovery period. Blood transfusions are also rarely needed. This type of joint replacement often results in more natural movement in the knee and you may be able to be more active than after a total knee replacement.

Talk to your surgeon about the type of surgery they intend to use and why they think it's the best choice for you.

Other procedures

In some cases, there may be other types of surgery you can have, including:

Kneecap replacement

If only your kneecap is damaged, an operation called a patellofemoral replacement or patellofemoral joint arthroplasty can be performed. This is a simpler surgery with a faster recovery time. However, the long-term results are still unclear and it's not suitable for most people with osteoarthritis.

Mini-incision surgery

This is usually used for partial knee replacements.

The surgeon makes a smaller cut than in standard knee replacement surgery. Specialised instruments are then used to manoeuvre around the tissue, rather than cutting through it. This should lead to a quicker recovery.

Read the NICE guidance on mini-incision surgery for total knee replacement.

Image-guided surgery

The surgeon performs this operation using computerised images, which are generated by attaching infrared beacons to parts of your leg and to the operating instruments. These are tracked on infrared cameras in the operating theatre. Results so far suggest that this may enable the new knee joint to be positioned more accurately.

Most hospitals don't yet have the equipment to do this and only around 1 in 100 knee replacements are performed in this way.

Patient-specific knee replacement

This is a more recent advance in knee replacement surgery. A guide is created using MRI scans. This helps to create the best fitting prosthesis for each patient.

The potential advantage is that the prosthesis may last longer, as the most accurate fitting is used. However, as this is a new technique, the results and long-term effects aren't fully known yet.

As with any operation, knee replacement surgery has risks as well as benefits. Most people who have a knee replacement do not have serious complications.

After having a knee replacement, contact your doctor if you get:

• hot, reddened, hard or painful areas in your legs in the first few weeks after your operation – although this may just be bruising from the surgery, it could mean you have deep vein thrombosis (DVT), which is a blood clot in the leg
• chest pains or breathlessness – although it's very rare, you could have a blood clot in your lung (pulmonary embolism) which needs urgent treatment

Anaesthesia

Anaesthetics are extremely safe, but carry a risk of minor (usually temporary) side effects such as sickness and confusion. There is also a slight risk of serious complications.

The risk of death in a healthy person having routine surgery is very small. Death occurs in around one in every 100,000 general anaesthetics given.

The risk is higher if you're older or have other health conditions, such as problems with your heart or lung.

Your anaesthetist and surgeon can answer questions you may have about your personal risks from anaesthetic or the surgery itself.

Other complications

Complications occur in about 1 in 20 cases, but most are minor and can be successfully treated. Possible complications include:

• infection of the wound – this is usually treated with antibiotics, but occasionally the wound can become deeply infected and require further surgery
• unexpected bleeding into the knee joint
• ligament, artery or nerve damage in the area around the knee joint
• DVT – clots may form in the leg veins as a result of reduced movement in the leg during the first few weeks after surgery. They can be prevented by using special support stockings, starting to walk or exercise soon after surgery, and by using anticoagulant medicines
• fracture in the bone around the artificial joint during or after surgery
• excess bone forming around the artificial knee joint and restricting movement of the knee – further surgery may be able to remove this and restore movement
• excess scar tissue forming and restricting movement of the knee – further surgery may be able to remove this and restore movement
• the kneecap becoming dislocated – surgery can usually repair this
• numbness in the area around the wound scar
• persistent pain in the knee
• allergic reaction – you may have an allergic reaction to the bone cement if this is used in your procedure

In some cases, the new knee joint may not be completely stable and further surgery may be needed to correct it.

How long will a replacement knee last?

Wear and tear through everyday use means your replacement knee might not last forever. Some people will need further surgery.

According to the National Joint Registry (NJR), around 1 in 20 patients who have a knee replacement will need further surgery after 12 years. However this depends on the type of replacement. Total knee replacements tend to last longer than partial knee replacements.

Find more information on how long knee implants last on the NJR website.

Recovery time can vary depending on the individual and type of surgery that's been done. It's important to follow the advice the hospital gives you on looking after your knee.

After surgery

In the surgical ward, you may be given a switch that enables you to self-administer painkillers at a safe rate. You may also be given oxygen through a mask or tubes. If necessary, you'll be given a blood transfusion.

You'll have a large dressing on your knee to protect your wound. A tube may be put in place after the surgery to drain blood from the operation site and prevent it collecting inside the wound.

Your wound dressing will be changed regularly until it's healed.

Read more information about what happens after an operation.

How soon will I be up and about?

The staff will help you to get up and walk about as quickly as possible. If you've had keyhole surgery or are on an enhanced recovery programme, you may be able to walk on the same day as your operation. Generally, you'll be helped to stand within 12 to 24 hours after your operation.

Walking with a frame or crutches is encouraged. Most people are able to walk independently with sticks after about a week.

During your stay in hospital, a physiotherapist will teach you exercises to help strengthen your knee. You can usually begin these the day after your operation. It's important to follow the physiotherapist's advice to avoid complications or dislocation of your new joint.

It's normal to have initial discomfort while walking and exercising, and your legs and feet may be swollen.

You may be put on a passive motion machine to restore movement in your knee and leg. This support will slowly move your knee while you are in bed. It helps to decrease swelling by keeping your leg raised and helps improve your circulation.

Going home

You'll usually be in hospital for 3 to 5 days, depending on what progress you make and what type of knee replacement you have. Patients who have a partial knee replacement usually have a shorter hospital stay.

If you're generally fit and well, the surgeon may suggest an enhanced recovery programme where you start walking on the day of the operation and are discharged within 1 to 3 days.

Read more information about getting back to normal after an operation.

Recovering at home

You may feel extremely tired at first and the muscles and tissues surrounding your new knee will take time to heal. Follow the advice of the surgical team and call your GP if you have any particular worries or queries.

After you're discharged from hospital, you may be eligible for up to 6 weeks of home help and there may be aids that can help you. You may also want to arrange for someone to help you for a week or so.

The exercises your physiotherapist gives you are an important part of your recovery. It's essential you continue with them once you're at home. Your rehabilitation will be monitored by a physiotherapist.

How long will it be before I feel normal?

You should be able to stop using your crutches or walking frame and resume normal leisure activities 6 weeks after surgery. However, it may take up to 3 months for pain and swelling to settle down. It can take up to a year for any leg swelling to disappear.

Your new knee will continue to recover for up to 2 years after your operation. During this time, scar tissue will heal and muscles can be restored by exercise.

Even after you have recovered, it's best to avoid extreme movements or sports where there's a risk of falling, such as skiing or mountain biking. Your doctor or a physiotherapist can advise you.

When can I drive again?

You can resume driving when you can bend your knee enough to get in and out of a car and control the car properly.

This is usually around 6 to 8 weeks after your surgery, but check with your physiotherapist or doctor whether it's safe for you to drive.

When can I go back to work?

This depends on your job, but you can usually return to work 6 to 12 weeks after your operation.

When can I do housework?

For the first 3 months, you should be able to manage light chores, such as dusting and washing up.

Avoid heavy tasks such as vacuuming and changing the beds. Do not stand for long periods as this may cause ankle swelling and avoid stretching up or bending down for the first 6 weeks.

How will it affect my sex life?

You may find that having the operation gives your sex life a boost. Your surgeon can advise when you can have sex again. As long as you're careful, it should be fine after 6 to 8 weeks. Avoid vigorous sex and kneeling positions.

Will I have to go back to the hospital?

You'll be given an outpatient appointment to check on your progress, usually 6 to 12 weeks after your knee replacement.

Will I need another new knee?

The knee can be replaced as often as necessary, although results tend to be slightly less effective each time. Recovery may take longer, but once you've recovered, results are usually good.

Looking after your new knee

• continue to take any prescribed painkillers or anti-inflammatories to help manage any pain and swelling
• use your walking aids but aim to gradually decrease the amount you rely on them as your leg feels stronger
• keep up your exercises to help prevent stiffness, but do not force your knee
• do not sit with your legs crossed for the first 6 weeks after your operation
• do not put a pillow underneath your knee when sleeping as this can result in a permanently bent knee
• avoid twisting at your knee
• wear supportive shoes outdoors
• do not kneel on your operated knee until your surgeon says you can
• raise your leg when sitting and apply an ice pack (or a bag of frozen peas) wrapped in a tea towel for 20 minutes every 3 or 4 hours to reduce any swelling