The development of hip and knee replacement surgery is one of the greatest successes of modern medical technology, and since the introduction of hip replacement surgery in the 1960’s and knee replacement surgery in the 1970’s, millions of patients worldwide have been given their lives back. Severe arthritis causes pain and disability, and can seriously adversely affect an individual's quality of life, and when the damage and the symptoms become bad enough to justify the pain, the hassle and the risks of the actual surgery itself, then joint replacement surgery can be an absolute God-send. Most patients are also concerned that they the timing is right to go for knee replacement surgery. Some people say that you should only ever have a knee replacement as a very last resort, and that the surgery should be delayed for as long as possible. This is not actually correct.
Getting knee replacement surgery right
Hip replacement surgery can, perhaps, be considered the gold-standard in the field of orthopaedic joint replacement surgery, with patient satisfaction rates in the region of 95%+. Knee replacement, on the other hand, is a somewhat more challenging operation, and the standard reported rates of patient satisfaction after knee replacement surgery are in the region of about 80 to 85%. This means that 15 to 20% of patients actually end up unhappy with their new knee, and with about 100,000 patients a year undergoing knee replacement surgery in the UK, this equates to a total of 15,000 to 20,000 unhappy patients every year, which is clearly a significant issue. This is perhaps why knee replacement surgery has a somewhat poor reputation amongst GPs and patients alike, compared to hip replacement. It is essential that any patient contemplating potential knee replacement surgery should be fully aware of the likelihood of ‘success’ and the potential risks of not actually ending up happy with their new knee. Of greater importance is to do some research and understand what can be done to help ensure a happy outcome.
Graham says, “The knee feels fantastic, not quite a year yet but I can hardly feel any difference between the two of them. I can exercise fully without any hint of pain or swelling. The transformation from a year ago is incredible. Still being careful not to overdo it but I feel so positive and rejuvenated! The only complaint has come from my wife about my terrible dad dancing now I am back on the dance floor!”
Greater variation in movement
There are a number of reasons why knee replacement surgery is more challenging. First, the hip is just a simple ball and socket joint, with only one movement: rotation. With the knee, however, there is flexion and extension (like a hinge), but there is also some side-to-side movement (varus / valgus), some sideways rotation (internal and external rotation) and some translation backwards and forwards (particularly on the outer side of the knee). In addition, there is also the patella (kneecap) at the front of the joint, which slides up and down in the trochlear groove at the front of the femur with knee flexion and extension. All of this makes for an extremely complex joint with very complicated biomechanics / kinematics that are difficult to replicate.
Individual differences
With a standard knee replacement, the prosthesis comes in different sizes, but with each make and model, the prosthesis is always the same shape (trying to replicate the ‘average’ knee). In reality, however, not only do patients come in different sizes, but the shapes / contours / proportions of a knee can also vary enormously between patients, with all of the different variables varying independently of each other. Therefore, if a standard off-the-shelf knee replacement prosthesis fits your knee, then its perhaps more luck than judgement. However, if you want a knee replacement prosthesis that fits you perfectly, every time, then the answer is to go for a custom-made prosthesis.
Significantly improving outcomes
Custom-made knee replacements, from an American company called Conformis / Restor3d) have been in use in the UK since 2012 (Mr McDermott was the first knee surgeon in the UK to implant a Conformis custom-made prosthesis), and published research shows that with a custom-made knee the patient satisfaction rates are as high as 90 to 95%. Importantly, one should not look at this as a roughly 10 to 15% improvement in outcomes; instead, what this actually represents is a reduction in the risk of a patient ending up unhappy by up to 75%! (from 20% unhappy, at worst case, with a standard knee, to 5% unhappy, at best case, with a custom-made knee), which is highly significant.
Officially lowest revision rates
In addition, the 2023 Annual Report of the UK National Joint Register reported that the 10-year revision rate for the Conformis iTotal knee replacement prosthesis was just 1.23%, compared to a figure of 5% for all knee prostheses on the register, and this revision rate represents the lowest revision rate ever reported for any knee prosthesis on the register.
How pre-hab and physio help
Importantly, even with success rates in the region of 90 to 95%, this means that there is still not a 100% guarantee that any individual patient will actually end up happy with their new knee. One important factor when discussing outcomes is to assess what factors from the patient themselves might influence outcome, and these factors include weight, psychological status (such as depression) and also expectations. Clearly, a patient who is unhappy with life in general will not simply be made happy overall just because they have a new shiny knee. Also, heavier patients who are less fit tend to have lower endorphin levels, and hence lower pain thresholds; therefore, if a patient is able to lose weight and get their cardio fitness levels up ahead of surgery (with ‘pre-hab’, with the help of a physio), then this can help on many levels.
Know your knee
In one particularly interesting study that was published looked at patients undergoing hip or knee replacement surgery. The patients were randomised into two groups: in the first group, patients attended a Hip / Knee School, whereas patients in the second group didn't.
At the Hip / Knee School, patients were shown a 15-minute video followed by them having a 15-minute one-on-one session with a physiotherapist. The study showed that those patients attending the Hip / Knee School pre-operatively ended up with higher satisfaction rates post-operatively, after their surgery. Importantly, when the authors of the study then analysed what factors most affected patient satisfaction rates, they found that the improved satisfaction for patients after attending the Hip / Knee School was largely related to a reduction in the patients’ pre-operative expectations! In other words, if a patient has false / unduly-high expectations ahead of surgery then, inevitably, they are less likely to meet them after surgery, and hence they are less likely to feel satisfied. This shows the critical importance of pre-operative patient information and education.
An absolute blessing
Importantly, even though an artificial joint is not exactly the same as one's own original perfect normal knee, a knee replacement prosthesis is much better than a painful stiff arthritic knee, and knee replacement surgery has been an absolute blessing for many many patients.
A custom-made knee prosthesis designed to perfectly match the size, shape and contours of each individual patient’s specific knee.
To book an appointment with Mr Ian McDermott
Further reading:
Read more: https://sportsortho.co.uk/testimonial/my-new-fantastic-knee/
And to find out more about Consultant Knee Specialist,
Mr Ian McDermott MB BS, MS, FRCS(Tr&Orth), FFSEM(UK)
Consultant Knee Surgeon, London Sports Orthopaedics
Professor Emeritus, London Southbank University
