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.

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.

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.

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.

On the day of your knee replacement operation, you'll meet your Consultant and Anaesthetist, who’ll answer any questions you have before we help you get ready for theatre.

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.

The surgery is usually carried out under a spinal (or epidural) 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.

The Signature™ knee replacement uses a 3D image (created by an MRI – Magnetic Resonance Imaging - scan) to design an alignment guide for a replacement knee joint that’s based on your specific anatomy. The guides which are specific to you and your Consultant will place these on the bone during the operation. The guide includes small holes through which the drills are passed. These drills remove a specific amount of bone before the joint replacement is attached.

Because the Signature™ is personalised, this means that the components of the replacement joint can be better seated and aligned; metal components won't overhang and irritate the ligaments and soft tissues and you should end up with a straight knee, a speedy recovery and good range of movement.

The knee replacement itself is a standard Vanguard knee replacement.

Signature™ is most often used if you have an abnormal leg anatomy, either due to how your bones have formed at birth or following a fracture which makes aligning a standard knee replacement more difficult.

With a standard knee replacement, your Consultant will take measurements from 2D weight-bearing x-rays. With a Signature™ knee replacement, they’ll take 3D MRI scans or CT scans at the hip, the knee and the ankle to give a full  understanding of your unique anatomy.

A special computer programme helps your Consultant analyse the scan to get a model of what your arthritic knee looks like, as well as how it's affecting the hip and the ankle. The software works out your knee’s mechanical alignment, how much bone needs to be taken during the operation and delivers a plan.

The Consultant reviews the images and can feed back to the software, for example, changing how much bone to take away to correct the deformity, until they are happy with the finalised surgical plan.

Signature™ mainly benefits patients who have a severe deformity of their thigh or shin bone.  During a standard knee replacement, the Consultant puts a guide rod down the middle of these bones during the operation to gain alignment and this is more challenging to perform with severe deformity but a  Signature™ knee replacement minimises this problem.

As the guide is more accurately sized for you, this should help reduce procedure time slightly. And because there’s less need to place surgical instruments in the thigh and shin bone to get measurements during the operation, there should be less interoperative trauma. This often helps with early recovery and should get you out of bed more quickly with less pain and swelling.

Not everyone is suitable for a Signature™ knee replacement. You should discuss your suitability with your Consultant Orthopaedic Surgeon.

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.