Published December 2022
The gold standard treatment for knee arthritis is a total joint replacement. Yet one in four who have this surgery are unhappy with results and continue to experience pain and discomfort. Dr Amy Garner, an orthopaedic surgeon, investigated whether combinations of smaller, partial knee replacements could be an effective alternative.
During my typical day in the operating theatre, I may perform four total knee replacements. One of those patients will likely go on to wish they never had the surgery and I believe we can do better than thisDr Amy Garner
Arthritis of the knee affects millions of people worldwide. The gold standard treatment is total knee replacement, with around 100,000 operations taking place each year in the UK.
While the majority of people are very happy after total knee replacement, one in four are dissatisfied due to ongoing pain, stiffness or because their new joint isn’t as good as they hoped. Despite being a common operation, total knee replacement is a major surgery and comes with significant risks in frail and older people, such as infection, bleeding, blood clots and even death.
Less extensive surgery, known as partial knee replacement, is available and evidence suggests it is a better option when arthritis is limited to certain areas of the knee.
What is the alternative to total knee replacement?
The knee is divided into three parts – inner, outer and under the kneecap – and it’s very rare to have arthritis in all three at the same time. Even though most people wear out just one part of their knee, a total knee replacement will remove the other healthy parts, as well as the ligaments that are vital for knee stability.
A partial knee replacement only replaces the specific part of the knee that is worn out, leaving the healthy parts and ligaments alone.
Partial knee replacements tend to be less common because the surgery is harder to do, requiring extra training. Another concern is that people with partial replacements will wear out another part of the knee over time, at which point they would need to undergo further surgery.
Is it effective to combine partial knee replacements?
During my typical day in the operating theatre, I may perform four total knee replacements. One of those patients will likely go on to wish they never had the surgery and I believe we can do better than this.
I wanted to know whether it’s feasible to do two partial knee replacements in a single operation, replacing only the worn parts and leaving behind the healthy part. I also wanted to know whether it’s helpful for patients to have a second partial knee replacement following a first one if another part of their knee develops arthritis. This would be instead of having a total replacement as their second surgery which removes the original partial knee replacement, which may be continuing to work well.
In contrast to total knee replacement, these approaches would leave the ligaments in place, which might make all the difference to how satisfied people are following surgery.
Testing knees in action and in the lab
People who had a combination of partial replacements could walk faster than those with total replacements – nearly as fast as healthy people – and they had a more normal walking pattern.
My PhD had several strands. Firstly, I measured how well 62 people with different kinds of knee replacements walked. Using a specially adapted treadmill, I looked at how quickly they could walk, how long their steps were and whether they could put normal pressure through the leg. I found that people who had a combination of partial replacements could walk faster than those with total replacements – nearly as fast as healthy people – and they had a more normal walking pattern.
Secondly, I used a questionnaire to ask the same group of people how happy they were with the outcome of their surgery. Those with combinations of partial knee replacement reported being much more satisfied and having an overall better quality of life than those who underwent a total knee replacement.
Finally, in the lab, I tested the biomechanics of each type of knee replacement. I performed knee replacements on donated, healthy knees from people who had passed away and then tested their movement and stability. I found that after a partial replacement, the knees were more stable and had more power than those after a total replacement. This suggests that activities such as standing up from a chair, walking up and down the stairs and kneeling would be much easier for patients after combinations of partial knee replacements, compared with those who underwent the full joint surgery.
What’s happening next?
There’s a growing interest in combinations of partial knee replacement, and I’m pleased to be contributing to these efforts.
I’ve shared my findings in over 20 conferences and won several prizes including the 2019 European Knee Society Arthroplasty Conference ‘Best Free Paper’ for Podium Presentation and 2021 British Association of Surgery of the Knee ‘Best Free Paper’ Annual Conference.
I’m coming to the end of my training to become a consultant in orthopaedic surgery, working towards a position that involves research and clinical practice side by side.
It was great to have the combination of theoretical science and hands-on operating in my PhD, thanks to a Clinical Research Fellowship jointly funded by the DMT and Royal College of Surgeons.