Over 70,000 knee replacements are carried out in England and Wales each year , a procedure that involves replacing the knee joint with an artificial one. Knee replacement surgery is most often carried out to treat pain caused by osteoarthritis though in some cases it may be used to treat a knee injury. If the knee is not put under too much strain, most artificial replacement joints will typically last for at least 20 years.
During knee replacement surgery, either the whole of the joint is replaced, known as a total knee replacement (TKR) or, in some cases, only one half, which is known as a unicompartmental knee replacement (UKR).
Although knee replacement surgery is often the best treatment for people with advanced osteoarthritis, before you make the decision to go ahead it’s important to:
Osteoarthritis (OA) of the knee is the most common form of arthritis, causing pain, swelling and stiffness. It’s caused by long term wear to the joint surface cartilage. Thanks to recent research into the causes of knee OA and its treatment, doctors are now able to offer a more effective approach to the management of this condition.
The most commonly affected areas of the knee are the medial and patellofemoral compartments:
Some people may have very advanced OA damage and feel very little pain, while others may have severe pain but with very little wear of the joint showing on an X-ray. When knee OA symptoms are very advanced, they can have a major impact on all areas of your life, including gentle exercise such as walking, and it can also affect sleep quality.
A diagnosis made during a medical consultation is usually backed up by X-rays that will show the extent of the damage. You may also be offered an MRI scan, if the diagnosis is not clear, to differentiate knee OA from other conditions, such as a meniscus tear.
We only advise our patients to have knee replacement surgery after other treatments have proved unsuccessful. These include:
Research carried out by the World Health Organization (WHO) has shown that patients who have the knowledge, skills and confidence to manage their own condition enjoy better outcomes.
Your experience of having knee replacement surgery is likely to be more positive if you:
The knee joint consists of the lower end of the thigh bone (femur) and the top of the shin bone (tibia); at the front of the knee is the knee cap (patella). The patella moves up and down in a groove on the front of the femur as the knee bends and straightens. All the surfaces of the bones are covered in articular (chondral) cartilage, which is a smooth, tough and rubbery surface that allows the bones in the knee joint to move easily against each other with minimal friction.
The bones are held together by ligaments and joint capsules; the meniscal cartilages help load-sharing and stability in the medial (inner) and lateral (outer) portions of the joint between the shin bone (tibia) and thigh bone (femur).
During total knee replacement surgery, both sides of the knee joint are replaced with artificial parts (prosthesis).
This type of surgery involves replacing only the worn part of the knee. Your consultant will be able to advise whether this is a better option for you than total knee replacement surgery. In this surgery:
All surgery carries risks and these will be discussed with you in detail. Complications following knee replacement surgery are rare. However, it’s important you understand these before you decide to go ahead. You’re more likely to have complications if you smoke, are obese or have other health problems.
The risks of knee replacement surgery are outlined below.
The chance of infection is less than 1% and can usually be treated effectively with antibiotics. Usually only the skin is affected, but if bacteria get into the knee itself then it may be necessary to have a further operation to wash it out with saline solution and give stronger antibiotics via a drip. On very rare occasions it may be necessary to remove the knee replacement completely to allow the bacteria to be treated. It’s then replaced, either during the same procedure, or after four – six weeks.
You can help prevent infection by keeping the wound clean and dry. You’ll be advised how to care for the wound before you leave hospital.
Blood clots can occur after any operation but are more likely to occur following lower limb orthopaedic operations. To reduce the risk of blood clots, you’ll be encouraged get up and walk around as soon after your operation as possible, often on the same day. We will also assess your risk of developing a blood clot and, in some cases, you’ll be prescribed blood thinning medication. You’ll also be given some foot and ankle exercises immediately after surgery and will also be advised to wear special socks for six weeks after surgery.
Deep vein thrombosis (DVT)
This is when a blood clot develops in the deep veins in the back of your lower leg; however, some swelling in the leg after surgery is very common. If you’re worried you have DVT, you should see a doctor as soon as possible. The risk of DVT is less than 1% and treatment includes blood thinning medication
Pulmonary embolism (PE)
This is when part of a blood clot that forms in the leg breaks away and is carried to the lung. The risk of this is extremely low (1 in 1000) and treatment is the same as for DVT (see above)
Small nerves that supply sensation to the skin near the operation site can be damaged, although the risk of this is small (less than 2%).
Loosening of the prosthesis
In most cases artificial replacements last at least 20 years.2 However, being overweight or overusing the joint will result in increased wear and tear. Loose or painful artificial joints can normally be replaced but, in some cases, the results of a second procedure aren’t as good as the first and the risks of the operation can also be higher.
There is a small risk of developing a medical problem following surgery. These include heart attacks, strokes and pneumonia. There is also a small risk of dying associated with this type of operation (nationally this figure is 0.4%). These risks will be discussed with you at the time of consultation with your surgeon.
You will be screened for bacteria and MRSA before your surgery to reduce the chance of an infection, and during your operation you’ll also be given intravenous antibiotics. If you’re concerned about the risks of surgery, please discuss this with your consultant and/or anaesthetist before you give consent for the operation.
Research has shown that patients who engage more with improving their own health and are well informed have better outcomes. There is more information about preparing for surgery in the next section.
The benefits of surgery include:
Depending on the kind of work you do, you may need up to six weeks off work. However, your consultant will be able to advise you about this as everyone is different and your rate of recovery may be different from other people’s. We normally recommend that you don’t work at all for the first two weeks, gradually returning to normal after four to six weeks (if your job mainly involves sitting down). Manual workers may need up to three months to return to normal.
The aim of surgery is to help you to return to your normal everyday activities without being in pain. This includes going up and down stairs, walking and non-competitive sports including:
An artificial knee isn’t the same as a normal knee and you should avoid overloading the joint. It’s also important not to take part in activities that will wear the joint or result in an injury so it’s best to avoid: