What is the Best Total Knee Replacement Option For Me?

4th March 2022 By Phoenix Hospital Group

Written by Mr Ian McDermott, Consultant Knee Surgeon at Phoenix Hospital Group

If you’ve been diagnosed with knee osteoarthritis and have been advised that you need a knee replacement, then you’ll probably want to research your options. There is a lot of information out there about the different types of knee replacement surgery and implants. As a result it’s often difficult to know which the best option is for you, personally. My approach is always to give my patients all the information they need to make a fully-informed decision.  If they ask me specifically about what knee implant is the best for knee replacement surgery, then my recommendation for nearly all patients is a Conformis custom-made knee. These precisely match the size, shape and contours of your own knee joint.

In this article, I’ve outlined some of the information that I provide to my patients to help them decide what prosthesis implant is best for them, and also my reasons for recommending Conformis.

Standard off-the-shelf knee replacement prostheses  

With a standard ‘off-the-shelf’ prosthesis, the prosthesis is one standard shape and comes in a range of sizes. If, however, the size of your particular knee falls in-between two size ranges, then you might end up with a prosthesis that is a bit too big or a bit too small for your knee. Also, importantly, different people can have very differently shaped knees.

If the shape and contours of your knee are close to average, then an off-the-shelf prosthesis might give a satisfactory fit and outcome. However, if the shape of your knee differs significantly, you might end up with a knee that does not fit correctly or move or feel right.

Patient satisfaction rates with a standard off-the-shelf knee replacement are about 80 to 85%. However, this means that 15 to 20% of knee replacement patients end up unhappy with their knee. To put this into perspective, there are about 100,000 knee replacements performed per year in the UK. This means that there are 15,000 to 20,000 patients unhappy with their knee replacement surgery every single year!

Advantages of a standard off-the-shelf knee prosthesis:

  • Cheaper than custom-made knee replacement

Disadvantages of a standard off-the-shelf knee prosthesis:

  • Standard shape may not fit the shape of your natural knee
  • Lower patient satisfaction rates

Robotic knee replacement surgery

In recent years several centres and implant companies have been pushing for the use of robotics for knee replacement surgery. A robot can help ensure that a knee replacement prosthesis is put in straighter and more accurately.

The issue with this is that those pushing the use of robotics are still using off-the-shelf prostheses. Whilst the robot allows you to put in something very accurately, the knee implant itself may or may not accurately match the size and shape of the patient’s knee. 

Advantages of robotic knee replacement:

  • Accurate placement of the prosthesis

Disadvantages of robotic knee replacement:

  • Slower surgery, with a significant learning curve for the surgeon
  • Accurate placement of a potentially ‘inaccurate’ off-the-shelf prosthesis
  • No evidence of any actual improvement in patient outcomes

Conformis custom-made knee replacement surgery  

With a custom-made knee replacement, each prosthesis is made to exactly match the size and shape of each patient’s knee. This is done by taking a high-res CT scan of your knee and using 3D technology (see image above). This then produces a prosthesis that fits your knee by design and that is bespoke specifically to you. This means that less bone has to be removed during the surgery. This is because, unlike off-the-shelf implants, you don’t have to cut the bone to match the prosthesis. There is also a higher probability that the new knee will move and feel more like your own natural knee. With a custom-made knee replacement, there is a significantly higher chance of ending up satisfied and happy with your knee.

The use of a robot isn’t required, because Conformis implants are tailored to the patient and come with 3D-printed custom-made cutting blocks. These patient-specific cutting blocks enable the surgeon to cut the bone with absolute precision, with exactly the correct angles and millimetres of bone resected, as per the detailed pre-operative plans provided for each case. Studies show that the accuracy of these cutting blocks is just as good as robotic surgery, but without the need for the additional equipment, expense and time required.

The patient satisfaction rates with a custom-made knee are 90 to 95%, demonstrating the clear superiority of the clinical outcomes of a custom-made knee compared to an off-the shelf prosthesis.

Price of a Conformis custom-made knee replacement:

So, are custom-made knees prohibitively expensive? No! – a Conformis custom-made knee prosthesis is only about £1,500 more expensive than a standard off-the-shelf prosthesis. The overall total cost of knee replacement surgery privately is in the region of about £15,000. Therefore, an extra 10% to have a better implant and a higher probability of a good outcome is well worth the money, and something that most self-paying patients are happy to pay for. Conformis custom-made knee replacements are covered by most UK private medical insurers.

Advantages of a custom-made knee replacement:

  • Specifically designed for the individual patient, with a perfect fit every time
  • Less bone needs to be removed during the surgery
  • Better kinematics (i.e. the knee moves more naturally)
  • Significantly better outcomes in terms of patient satisfaction 


So, what is the best total knee replacement option for patients?

Having a total knee replacement operation is a big decision for any patient. That’s why it’s so important that patients are given all of the information that they need to make a fully-informed decision about what the best option is for them, as an individual. Based on the advantages and disadvantages of the different types of implant, as outlined above, my recommendation for almost every patient nowadays is a Conformis custom-made knee.

Conformis custom-made total knee replacement surgery at Phoenix Hospital Group

At Phoenix Hospital Group, patients can have total knee replacement surgery using Conformis customised implants under the expert care of Mr Ian McDermott, Consultant Knee Surgeon. Mr McDermott was the first surgeon in the UK to implant a Conformis G2 custom-made knee. He is one of the most experienced consultants in the UK offering this type of partial and total knee replacement surgery.

Mr McDermott runs regular clinics at our outpatient centre at 25 Harley Street. For patients requiring surgery, he operates at Weymouth Street Hospital.

To arrange an appointment to see Mr Ian McDermott, or to enquire about the cost of having Conformis knee replacement surgery at Phoenix Hospital Group, you can call us on 0207 079 2100 or email: appointments@phoenixhospitalgroup.com.

For more information about Mr Ian McDermott, visit his website:  www.kneesurgeon.london