A landmark study of partial knee replacement implants commissioned by YKC’s Nick London has exploded the last remaining myth of mobile-bearing partial knees and confirmed that “there is now no one single advantage of mobile bearings over fixed”.

But what does that mean if you’re exploring knee replacement options – or if you’re already walking around on a knee implant that uses a mobile bearing? Here, Nick explains.

If you’re buying a piece of equipment for the home – a fridge, a television or washing machine, for example – there’s a good chance one question about your new purchase will assume greater importance than almost any other: how long will it last?

When it comes to knee replacement (more correctly called knee resurfacing) that question becomes even more important. Every piece of mechanical equipment has a lifespan and a knee implant is no different. What is different is that ‘fixing’ or replacing a worn implant is rather more complicated than replacing the washing machine.

It’s vitally important, therefore, that the implant that goes into your knee is as durable as it can possibly be.

Mobile vs fixed bearing partial knee implants

As I explore in this post, knee implants essentially comprise three parts: two metal components that cap (or resurface) the worn ends of the thighbone and shinbone, and a bearing that sits between them which enables the joint to move like a natural knee.

There’s an enduring myth that fixed bearings aren’t as durable as their mobile counterparts, a myth that we clearly expose and discredit in a new study which examines wear and implant revision rates (that is, ‘rework’ surgery performed when implants wear out) using independent data from global studies and the world’s joint registries.

> Read the study

The study finds that there is no evidence from the last 25 years to support an advantage for mobile-bearings in terms of wear. What’s more, evidence from laboratory studies indicates that mobile-bearings have MORE wear than fixed. All of which means that there is now no one single advantage of mobile bearings over fixed bearings.

So where does that leave you if you’re considering having a partial knee replacement? And, perhaps even more importantly, what (if anything) should you do if you’ve already had a partial knee replacement that uses a mobile bearing, such as the Oxford partial knee implant?

What to do if you’ve already had a mobile bearing implant

It’s important to say that, for the majority of well-selected patients (that is, patients suitable for partial knee replacement – because not every patient is) any implant will be a better option than a total knee replacement in terms of function.

For individual patients, the chance of your partial knee implant lasting many years – even with a mobile bearing – is high and the chance of complications is relatively small. It’s only when we look at hundreds or thousands of patients that we see the differences between implants.

The study doesn’t find that mobile-bearings make for a bad implant, so I certainly wouldn’t advise you consider having anything done to it. It’s just that the evidence tells us there are better options.

This remains true if you’ve already had one knee replaced and are having your other done soon. There’s no reason not to have your next partial knee using a fixed bearing implant, even if there’s already a mobile bearing in your other knee.

Implant bearing: how to talk about it with your knee surgeon

If you’re considering partial knee replacement, ask your knee surgeon about the implant they are planning to use. If they say it’s a mobile bearing implant, ask them why they’re making that choice when more and more evidence is coming out that fixed is better than mobile.

And of course, as a private surgery knee patient, you are perfectly free to look elsewhere if you’re not comfortable with the response, because the evidence is clear: for partial knee resurfacing, you should start with the fixed bearing.

How long will your partial knee replacement last? Read more

Talk to us about your partial knee replacement.