What is total knee replacement surgery?

Total knee replacement surgery is a successful operation used to replace the human knee joint when it's worn out due to osteoarthritis or from trauma that has caused it to wear out sooner rather than it should. It's a successful procedure, but it should only be done when the patient's knee is so painful that their quality of life is on the slide and their mobility is affected.

How long does a knee replacement last?

A total knee replacement hopefully will last at least 15 to 20 years. There are several variables that can determine the longevity of a knee replacement. They are out of everybody's control but everything being equal, it should last about 15 to 20 years.

Total knee replacement surgery replaces your damaged knee joint with an artificial joint. A unicompartmental knee replacement, also known as a partial knee replacement, replaces only part of your knee with an artificial joint.

A knee replacement operation (arthroplasty) is usually only recommended after non-surgical knee treatments such as pain relief, therapy and muscle strengthening have been tried first. 

A total knee replacement is recommended if your knee is badly worn and damaged, affecting your mobility and causing significant pain.

In a healthy knee, the surfaces of the joint are lined with cartilage which helps it move smoothly and easily without pain. When the knee joint surfaces become worn, your normal movement can become painful as the ends of the bones start to rub or grind together and the joint becomes stiff and inflamed.

There are many reasons why the joint lining can become worn or damaged:

Osteoarthritis in your knee

Osteoarthritis is a degenerative condition and is the most common reason for knee replacement surgery. This occurs when the cartilage wears down and the bones within the joint rub against each other. This leads to increasing pain and can restrict movement of the knee joint. Some patients also experience crunchy, creaky knees - especially when going up and down the stairs.

The bones may compensate by growing thicker and producing bony outgrowths to try to repair themselves. This can cause more friction and pain.

It’s estimated that about eight million people are affected by osteoarthritis in the UK. The main risk factors for developing osteoarthritis of the knee are:

• Obesity
• Being over 50 years of age
• Previous knee injuries

Rheumatoid arthritis

This is where the body’s own immune system (the body’s defence against infection) affects the lining of the joint in the knee, resulting in stiffness and pain.

Traumatic arthritis

This results from a serious knee injury such as a fracture, ligament damage or meniscus tear. The impact of the accident also causes ‘mini trauma’ to the cartilage which, over time, develops into osteoarthritis which causes knee pain and stiffness. If non-surgical knee treatments such as muscle strengthening haven’t worked, you might need to consider a total knee replacement.

In a healthy knee the surfaces of the joint are lined with cartilage which helps it move smoothly and easily without pain. When the knee joint surfaces become worn, your normal movement can become painful as the ends of the bones start to rub or grind together and the joint becomes stiff and inflamed.

There are many reasons why the joint lining can become worn or damaged:

Osteoarthritis in your knee

This occurs when the cartilage wears down and the bones within the joint rub against each other. This leads to increasing pain and can restrict movement of the knee joint.

The bones may compensate by growing thicker and producing bony outgrowths to try to repair themselves, this can cause more friction and pain. Osteoarthritis is the most common reason for knee replacement surgery.

Rheumatoid arthritis

This is where the body’s own immune system (the body’s defence against infection), affects the lining of the joint in the knee, resulting in stiffness and pain.

Traumatic arthritis

This results from a serious knee injury, such as a fracture, ligament damage or meniscus tear. The impact of the accident also causes mini trauma to the cartilage which, over time, develops into osteoarthritis which causes knee pain and stiffness. If non-surgical knee treatments such as muscle strengthening have not worked, a total knee replacement may be necessary.

Replacing both knees together isn’t common practice and, at Benenden Hospital, we don’t operate on both knees at the same time.

A knee replacement is a major operation and can cause quite a lot of stress to the body. If you have underlying medical conditions, you may be at higher risk of complications during anaesthetic, breathing problems, heart problems or blood clots – so it’s better to minimise the impact on your body by doing one procedure at a time.

If you have severe arthritis of both knees, we’d do staged operations, with the worst knee first. Once you’ve recovered, at around six weeks, we’ll talk to you about planning to replace the other knee three to six months later.

Knee replacements are either fixed to the bone with cement or are uncemented. Uncemented replacements rely on the body to grow bone into the knee replacement. After around nine months to a year, the knee replacement is fixed strongly to the bone.

A cemented replacement will be as strong as it’s going to be by the time the operation is finished.

Your Consultant will discuss your medical history and look at how well you move and the strength of your muscles. They’ll also view x-rays of the knee joint damage and look for exposed bone on bone in at least one knee compartment, before recommending the best course of treatment. Knee replacement surgery will only be recommended after you’ve tried non-surgical treatments such as changing your lifestyle, losing weight, taking pain relief or physiotherapy.

If you’ve agreed that total knee replacement surgery is the best treatment, your initial consultation might include tests and diagnostic imaging (x-rays or MRI scans). We may also be able to assess your fitness for anaesthesia on the same day, to reduce the number of visits you need to make to the hospital.

Your Consultant may recommend that you start an exercise programme to strengthen your muscles around the knee joint and increase flexibility before surgery as this can shorten recovery time after your operation.

What are the different types of knee replacement?

The various types of knee replacement include the unicompartmental knee replacement, and that's used to replace just one compartment of the human knee joint. Usually, the medial or inside compartment.

You can also get the lateral unicompartmental knee replacement, but that's used less frequently. To be able to use those two knee replacements, the disease needs to really be isolated to those two compartments.

The second type of knee replacement is the total knee replacement, and that's used when two out of the three at least compartments of the knee are worn out. It also gives the surgeon the option to replace the patella as well and that deals with all three compartments of the knee.

Benenden also has the ROSA robotic surgical tool which is used to help the surgeon perform total knee replacement surgery. ROSA stands for robotic orthopaedic surgical assistant and it’s a useful adjunct for the surgeon. It helps the surgeon plan the operation pre-operatively and intraoperatively to provide, hopefully, a more accurate, comfortable total knee replacement.

What happens during knee replacement surgery?

So total knee replacement surgery is an operation where the patient is sedated and anesthetised with a spinal anaesthetic. The knee is opened up and the worn-out surfaces are removed using instrumentation. This resurfaces the human knee joint with a metal femoral component and a tibial base plate that was just placed at the top of the shin bone or tibia bone in between the two. A plastic insert is fitted which acts as the new cartilage for the knee joint. The knee joint itself is balanced by your own natural ligaments.

How long does knee replacement surgery take?

The time a total knee replacement takes to be carried out depends on the complexity of the problem beforehand. But the average time is usually about an hour.

The surgery is usually carried out under a spinal anaesthetic. This is when an anaesthetic is injected into your lower back (between the bones of your spine) making the lower part of the body numb so you do not feel the pain of the operation and can stay awake. During your spinal anaesthetic you may be fully awake or sedated with drugs that make you relaxed but not unconscious.

Your surgeon will make a midline incision into the knee through which they'll perform the surgery. The worn bone will be removed and an artificial joint implanted and fixed with bone cement. The wound will be closed with absorbable sutures or skin clips and a pressure dressing applied.

After surgery we’ll move you to our recovery room for observation until you’re ready to return to the ward, where you’ll be looked after by our experienced nursing team. Your Consultant will advise when you can start your recovery with our expert physiotherapy team.

A total knee replacement operation typically takes no longer than two hours, including anaesthetic, but it’ll depend on the complexity of the operation, the severity of your arthritis, and your physique or build.

How long does it take to recover from a knee replacement?

A total knee replacement is a painful procedure, and the recovery is a lengthy one. The first six to eight weeks is tough going. It is uncomfortable and you need to really work hard on getting a range of motion in your artificial knee. Whilst the wound at the front of the knee heals up. So, it's absolutely essential that you have good pain control and a good quality physiotherapist. Full recovery can take up to about a year, but life returns to relative normality by about three months, usually.

How soon after a knee replacement can I drive?

After approximately six weeks, you can drive after receiving a knee replacement.

Can I run after a knee replacement?

So, activities following knee replacement depend on how well you've recovered from the operation and the range of motion you've achieved and the strength you've managed to attain in your leg. After about two months or so, it is hoped that you'll be able to get back to activities such as swimming, cycling, doubles tennis, squash. Some even get back to going to more athletic pursuits like skiing, but that's at their own personal risk. With regard to running, I wouldn't advocate this. However, it is known that some go for short jogs.

Can I kneel after a knee replacement?

Kneeling after a total knee replacement is a personal choice. I personally wouldn't advise it, but I know it has been done and you need to make sure you pad out the floor before kneeling on it.

How long it takes to recover will vary depending on your general health and fitness and the type of knee surgery you’ve had. We’re advocates of the Rapid Recovery Protocol; a multi-disciplinary approach which includes the Anaesthetist, Physiotherapists, Surgeon and nursing staff. We use this approach to minimise pain and help you recover as quickly as possible.

Your hospital stay

As a rule, you’ll spend two to three days in hospital and during that time your knee will be sore. You’ll have a large protective dressing on your knee, and you may have a drain to remove blood from your wound.

While you're staying with us, any pain will be controlled with the medication. You’ll be cared for by a highly skilled team of nurses and visited daily by our physiotherapy team who’ll help you regain your mobility through carefully planned exercise.

Going home

We’ll only let you leave hospital once we're happy that it’s safe for you to do so. We’ll give you a frame or crutches to start with and you'll be shown how to safely go up and down the stairs. After about a week most people can walk independently with sticks.

Your recovery

For the first two weeks, while the metal clips and staples are holding the wound closed, your knee might feel a bit bruised.

By six weeks, most people have turned the corner; the pain is still there but less intense. You may be able to cope on less strong painkillers. You should be able to walk around at home, or outside briefly, and drive your car for a short distance. You must continue to do your exercises in order to keep your knee replacement moving. We’ll invite you back to the hospital and see one of the Orthopaedic Surgeons to make sure that the wound has healed, and you have a good range of motion in your knee.

By three months, when you come back to the clinic, you’ll be able to feel the benefit of the operation. However, it may take another six months to make a full recovery and return to your normal activities. Following your Consultant’s advice on how to look after your new knee and sticking to the exercises given to you by your Physiotherapist are important aspects of the recovery process, and it's important to follow their guidance.

If you don't have any pain from the knee replacement then once the knee replacement has fully settled down, it’s fine to use a vibration plate. However, if the muscles around your knee become aggravated, and you start feeling pain when using the vibration plate, you should stop.

The best exercises to do at the gym following a knee replacement are ones that build up the thigh muscles, the quadriceps and the hamstrings. These will help keep the knee replacement stable in the long term.