A partial knee implant with a fixed bearing or a mobile one: which is better? A landmark new study commissioned by YKC’s Nick London finds one clear winner: “The best fixed-bearing partial knee implants are better than the best mobile-bearing implants.”

If you’re one of the many patients whose osteoarthritis affects only one of the three compartments in the knee, you may well be suitable for a partial knee replacement (more correctly called partial knee resurfacing). As we’ve explored many times, there are many reasons to choose partial knee resurfacing over total. Yet when you do, you may be faced with another decision – the implant.

What’s in a knee implant?

All knee implants feature broadly similar components. Your knee surgeon will cap the worn ends of the shinbone (tibia) and thighbone (femur) with metal. This resurfaces the bones – hence the name of the procedure. Between the two metal surfaces sits a polyethylene bearing that provides the surface on which the tibial and femoral components glide. This can be fixed, with the polyethylene bearing clipped into the tibial component so that just the femoral part can glide upon it. Or it can be mobile, with the bearing loose between both components.

A brief history of implant bearings

Knee replacement has advanced significantly over the past 25 years or so. Around the turn of the millennium, you may have heard it said that mobile bearings held an advantage over fixed because, some claimed, patients with implants that employed a mobile bearing would experience less implant wear. That would, in turn, supposedly result in long-term advantages such as reduced revision rates (that is, ‘rework’ surgery performed when implants wear out) and longer lasting implants.

I was never convinced by the evidence for this and yet, for numerous reasons (some of which we’ll explore below) the narrative persisted that fixed bearing implants were inferior. That remained the case even as production processes evolved to make the fixed polyethylene bearing exceptionally hard wearing.

Examining the evidence

To resolve the fixed vs mobile debate and to understand the reality of fixed bearing implant performance, I commissioned a study which looked specifically at bearing wear and implant revision rates using independent data from a multitude of global studies and the world’s joint registries since 2000.

The study also examined:

Implant performance in the lab and in clinical studies
Cemented and uncemented implants

This is what we found: the best performing fixed bearing implants have a lower revision rate than the best performing mobile bearing across all age groups and there is absolutely no evidence to support the claim that mobile-bearing implants (such as the Oxford partial knee, a mobile-bearing implant in widespread use) have any advantage in terms of wear.

> Read the study

To be clear, this study and other recent studies didn’t find that the best fixed bearings are merely as good as mobile bearings. Laboratory studies showed that the wear rate may actually be higher with mobile bearings than fixed, meaning that, across every parameter, the best fixed bearings perform as well as or better than mobile bearings. All of which means that there is now no one single advantage of mobile bearings over fixed.

The myth of mobile

Conventional wisdom is a pervasive thing. It’s hard to change once a position becomes entrenched. As I wrote in a LinkedIn post in 2025:

“In the 80’s key opinion leaders in the US precipitated a global collapse in the usage of partial knee surgery worldwide due to revision rate concerns. It has taken decades to recover from those opinions (and the USA still hasn’t to any great degree).”

It’s still the case that some knee surgeons will recommend a mobile bearing because of the power of the mobile myth. And I still speak to patients who say, “I’ve been told I should ask for a mobile bearing.”

Yet the evidence of this study suggests that there really is no reason why a patient or a surgeon should choose a mobile-bearing partial knee replacement over a fixed-bearing partial knee replacement.

Start with the fixed bearing

You may have questions about the above. If you’ve had a partial knee replacement using a mobile bearing, you may have concerns about the above, which I address (and hopefully allay) in this post.

But if you are a patient considering partial knee replacement/resurfacing or a surgeon starting your partial knee career, there is absolutely no doubt: 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.