Total knee replacement: when it is done, recovery and how long it lasts

The knee normally moves smoothly because the ends of the bones are covered with a layer of tough cartilage. The NHS explains that if the cartilage is worn away by osteoarthritis or damaged by an injury, the bones rub against each other and the joint becomes painful and stiff. In a knee replacement the damaged parts are replaced with metal and plastic parts.

NICE says most people who need a joint replacement have osteoarthritis, which affects up to 9 million people in the UK, and that people are usually offered a replacement only after other treatments such as pain medication, physiotherapy and lifestyle advice have not helped. The NHS adds that knee replacements are usually very successful and result in no pain in the knee and better movement.

Versus Arthritis says four out of five people who have had knee replacement surgery are happy with their new knees, and that for those who are not, the main cause is continuing pain that may not be due to a problem with the operation. It also says a replacement knee can never be quite as good as a natural knee: most people rate it about three-quarters normal, and most are not designed to bend as far as a natural knee.

The NHS says it may take several months or longer to recover fully, depending on your age and general health, and that recovery for a partial replacement should be shorter. Nurses and physiotherapists help you start walking soon after the operation, and you will need crutches or a walking frame at first. You are usually given compression stockings to prevent blood clots, which most people wear for at least 6 weeks.

Versus Arthritis says pain from bruising is normal in the first two months and that you will probably still need painkillers at six weeks to help you sleep, with some pain possible for as long as six months. Swelling, particularly around the ankle and foot, is very common and may last for up to three months or so. If you still have pain after six months, it advises speaking to your physiotherapist or GP.

The NHS recommends using crutches or walking sticks at first and reducing to one crutch then a stick as you gain confidence, following the exercises your physiotherapist recommends, keeping your leg raised as much as possible to reduce swelling, and avoiding twisting your knee, bending down and reaching up as much as possible.

It advises not sitting with your legs crossed for the first 6 weeks, not sleeping with a pillow under your knee, not kneeling on the new knee until your doctor says you can, and not standing for long periods because this could cause swelling in your ankles. Versus Arthritis says it is usually possible to kneel, but some people find it uncomfortable to put weight on the scar at the front of the knee.

The NHS says non-surgical treatments are normally tried first. They include weight loss to reduce strain on the knee if you are overweight, low-impact exercise such as swimming, walking or cycling with knee strengthening, walking aids, special footwear or insoles, pain relief medicines, gels or creams, and steroid injections into the joint.

If those have not helped, the NHS says other operations may be an option for some people: arthroscopy to clear out loose bone and cartilage, osteotomy to change the shape of the shin bone and reduce pressure on the worn part, microfracture, and scaffold insertion to help new cartilage grow. Versus Arthritis says non-surgical measures generally do not give results as good as a new knee joint but may allow you to delay replacement for some years.

The NHS says a total knee replacement, which replaces the lower end of the thigh bone and upper end of the shin bone, is the most common type. A partial knee replacement is used when arthritis affects one half of the knee. Versus Arthritis lists four main types: total, unicompartmental (partial), kneecap replacement (patellofemoral arthroplasty) and complex or revision replacement.

Versus Arthritis cautions that people who have partial knee replacements are more likely to need the knee revised than people with a total replacement: about 1 person in 10 needs further surgery after 10 years. Your surgeon will advise which suits your knee, age and general health.

You usually go into hospital on the day of the operation. The NHS says you will have either a general anaesthetic or a local anaesthetic in your spine, which leaves you awake but with no feeling from the waist down, and that the operation usually takes about 1 to 2 hours.

In a total knee replacement the surgeon cuts down the front of the knee, moves the kneecap to the side, cuts away the damaged ends of the shin and thigh bones and fits new parts over both. Some people also have the back of the kneecap replaced. The wound is closed with stitches or clips and covered with a dressing and bandage.

After surgery you will be asked whether you consent to your details being given to the National Joint Registry, which monitors knee replacements to help improve patient safety, experience and outcomes.

The NHS says preparation can include exercises to do before and after the operation, stopping smoking, a healthy diet and managing your weight, and that these matter while you wait because waiting lists can be long. You may be asked to attend a pre-admission clinic a few weeks beforehand for tests such as a blood test and blood pressure check, and to meet the team.

Plan for coming home: ask for help with day-to-day activities, keep things you use often within reach, stock the freezer with cooked meals, arrange transport because you will be unable to drive for several weeks, and talk to your employer about returning to work.

The NHS calls knee replacement a common and safe procedure and says most people have no complications; if there are any they are usually minor and can be treated. Risks depend on your age and general health.

Blood clots in the leg (DVT) are possible after surgery. The NHS says this is often not serious but a clot can sometimes travel to the lungs (pulmonary embolism), so you may be given compression stockings or anticoagulant medicines. Versus Arthritis says wound infection happens in about 1 in 50 cases and a deep infection in about 1 in 100, and that fewer than 1 in 100 patients have nerve damage, which usually improves gradually. Other possible problems include difficulty bending the knee, ongoing pain and stiffness, and the knee feeling unstable.

The NHS says most knee replacements last about 25 years and that needing another replacement later in life is not common. Versus Arthritis says a replacement joint may wear out or become loose after a time, and that most will last for 20 years or more, so younger people are more likely to need a repeat operation at some point.

Versus Arthritis says the chances of needing repeat surgery are increased if you are overweight, do heavy manual work, or run or play high-impact sport.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have recently had a knee replacement and you have throbbing or cramping pain in your leg, a high temperature or feel hot, cold or shivery, oozing or pus from your wound, or redness, tenderness, swelling or pain in your knee that is not getting better or is getting worse. These could be signs of infection or a blood clot.

Call 999 or go to A&E if you have pain and swelling in your leg and you are having difficulty breathing or have chest pain, which could be a blood clot in the lungs.

On the NHS a knee replacement usually follows GP care and a referral to an orthopaedic team once non-surgical treatment has not worked. Waiting times vary, which is why the NHS stresses preparing during the wait. Some people have the operation privately, usually for speed or choice of surgeon.

Whichever route you take, ask about the type of knee replacement being offered, the surgeon's experience, what rehabilitation is included and what happens if complications arise after you go home.