Friday, August 21, 2026

Robotic assisted knee replacement gives the same patient outcomes as a surgeon only procedure

Robot-assisted knee replacement surgery is more precise than a surgeon on their own, but does not currently lead to improvements in patient outcomes

University of Warwick

Mako Robotic System in Use — image:
Mako robotic system in use. Credit: UHCW NHS Trust
view more
Credit: UHCW NHS Trust

Robot-assisted knee replacement surgery is more precise than a surgeon on their own, but does not currently lead to improvements in patient outcomes, according to the RACER-Knee trial, the world's largest clinical study of its kind. This trial makes an important contribution to the evidence on robotics in health care and where future advances and research should focus. The trial, coordinated by the University of Warwick and University Hospitals Coventry and Warwickshire (UHCW) NHS Trust, is published in The Lancet, the world's oldest and best-known general medical journal.

Robotic assistance is increasingly used in knee replacement surgery worldwide, in six per cent of procedures in the UK, compared with 16 per cent in the US and 42 per cent in Australia, with the aim of helping surgeons place the knee replacement more precisely and tailoring surgery to a patient’s anatomy.

The National Institute for Health and Care Research (NIHR) funded the UK-wide RACER-Knee trial in partnership with Stryker, who make the robot that was tested. It was led by the Warwick Clinical Trials Unit, UHCW NHS Trust and the Royal Orthopaedic Hospital in Birmingham. It is the world's largest double-blinded randomised control trial comparing conventional total knee replacement to surgery assisted with the Stryker Mako robotic system, the most widely used system globally.

The trial found that one year after surgery, patients in both groups had similar recovery, mobility and pain levels. While robotic assistance was more precise, it did not translate into improvements in patient outcomes within the first year after knee replacement. The trial also found that robot-assisted knee replacement was not linked to an increased risk of serious adverse events, suggesting it was as safe as the usual approach to surgery.

The study was led between two Chief Investigators in the UK, they said:

Professor Andrew Metcalfe, Warwick Medical School, University of Warwick, and Consultant Orthopaedic Surgeon at UHCW NHS Trust: “We are delighted to have completed this world-leading randomised trial of an exciting technology that is now being used globally and at scale. It is an important step in the process of innovation and will stimulate lots more high-quality studies. We are very grateful for the support of the many patients who took part which is so important, but also the NIHR and Stryker for working so well together to support this critical study. Technology such as this could really help the care we give for patients, but for robotic-assisted knee replacements, there is still work to do before we see benefits such as less pain or better movement.”

Professor Edward Davis, Consultant orthopaedic surgeon at The Royal Orthopaedic Hospital NHS Foundation Trust and Honorary Professor at University of Birmingham: “The trial demonstrates robotic-arm-assistance allows for higher precision, and in theory the system should allow surgeons to customise the procedure according to a patient’s anatomy. These results are by no means a condemnation of the robotic systems, but more understanding of the ideal position for a knee replacement and personalisation for each patient is needed. We’ll then be able to truly take advantage of the advanced precision of robotic systems. “

Professor Anthony Gordon, Director for the NIHR Health Technology Assessment (HTA) Programme, said: “Innovation in healthcare depends on evaluating promising technologies rigorously and at scale. While this study shows robotic-assisted knee replacement is not yet improving patient outcomes, it highlights opportunities to refine these technologies and harness their precision to deliver better care in the future. The NIHR continues to fund robust studies, such as RACER, ensuring we learn how to deliver the latest technologies most effectively within the NHS.”

Total knee replacement is one of the most common elective operations worldwide for treating knee arthritis. Conventionally, surgeons rely on their experience and a standard set of instruments to perform the procedure. Some surgeons now use a robotic arm, controlled by the surgeon, to assist in the operation. The system positions instruments with high precision and gives surgeons greater flexibility to vary cutting angles and depths, enabling personalised approaches tailored to individual patient’s anatomy in ways conventional surgery cannot achieve.

339 patients from 10 hospitals, under the care of 33 surgeons across the UK, took part in the trial. Despite the potential advantages of robotics, the trial found that there was no meaningful difference in the primary measure, the Forgotten Joint Score, 12 months after the operation. The score measures the extent to which patients are aware of their artificial joints during daily activities, and patients showed equal results with their artificial joints, whichever method was used for doing the replacement. Patients also showed comparable outcomes in their ability to walk, their experience of pain in the first three months and at 12 months, their pain in hospital, and the likelihood of a follow-up operation.

The researchers will continue to follow-up patients for ten years to find out if there are any long-term differences between the two approaches. Importantly this might find out if there is a difference in number or patients needing more surgery for their knee.

Robotic TKRs took longer to perform (on average 10.5 minutes) and were around £950 more expensive on average, but were more precise and were not associated with an increased risk of serious adverse events, suggesting the robotic procedure was as safe as conventional surgery. Under current NHS cost limits, the robotic system tested in this trial was not cost-effective over the first year after surgery.

In the future, if the use of robotic assistance could help surgeons to better tailor to each patient's individual anatomy, then the robotic system's better precision could become worthwhile. This would need more development and further research but is an exciting area for future studies.

ENDS

The results of the RACER-Knee trial have published in The Lancet. DOI: 10.1016/S0140-6736(26)00986-4

Notes to Editors

For more information please contact:

Matt Higgs, PhD | Media & Communications Manager (Warwick Press Office)

Email: Matt.Higgs@warwick.ac.uk | Phone: +44(0)7880 175403

About the Trial

This research has been organised by University Hospitals Coventry and Warwickshire NHS Trust, and the University of Warwick. It has been funded by the UK NHS research body, the National Institute for Health Research, through its Health Technology Assessment Programme (NIHR128768)

Stryker, the manufacturers of the robotic system, met the additional costs of doing robotic surgery within this study. They were not involved in the analysis or interpretation of the study findings.

About the University of Warwick

Founded in 1965, the University of Warwick is a world-leading institution known for its commitment to era-defining innovation across research and education. A connected ecosystem of staff, students and alumni, the University fosters transformative learning, interdisciplinary collaboration, and bold industry partnerships across state-of-the-art facilities in the UK and global satellite hubs. Here, spirited thinkers push boundaries, experiment, and challenge convention to create a better world.

About University Hospitals Coventry and Warwickshire NHS Trust

University Hospitals Coventry and Warwickshire NHS Trust (UHCW) are one of the largest acute teaching Trusts in the UK, comprising University Hospital in Coventry and the Hospital of St Cross in Rugby and working in partnership with Warwick University Medical School and Coventry University. It has more than 11,000 staff and delivers services across the West Midlands region. This includes hosting region-wide services such as the Coventry and Warwickshire Pathology Network and Bowel Cancer Screening programme. The Trust works closely with its partners in health and social care in Coventry and Warwickshire to develop patient-focused services that meet the needs of our communities.

About the Royal Orthopaedic Hospital NHS Foundation Trust

The Royal Orthopaedic Hospital NHS Foundation Trust is one of the largest specialist orthopaedic units in Europe, offering planned orthopaedic surgery to people locally, nationally, and internationally. The Trust is an accredited Veteran Aware organisation and a Disability Confident Leader. A national centre for bone cancer and musculoskeletal medicine, the Royal Orthopaedic Hospital has a vibrant research portfolio of clinical trials, observational studies and laboratory studies exploring new treatment options, new approaches in rehabilitation and therapy, and new medical devices. This research is delivered by our researchers and clinicians spread across the Knowledge Hub, our home for education and research, and the Dubrowsky Regenerative Medicine Laboratory.

About NIHR

The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research. The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research.

We do this by:

funding high quality, timely research that benefits the NHS, public health and social care
investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services
partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research
attracting, training and supporting the best researchers to tackle complex health and social care challenges
collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system
funding applied global health research and training to meet the needs of the poorest people in low- and middle-income countries

NIHR is funded by the Department of Health and Social Care.

Our work in low- and middle-income countries is principally funded through UK international development funding from the UK government.

Journal

The Lancet

DOI

10.1016/S0140-6736(26)00986-4

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Robotic-arm-assisted versus conventional total knee replacement (RACER-Knee): a pragmatic, multicentre, participant-masked and assessor-masked, superiority, randomised controlled trial

Article Publication Date

20-Aug-2026

Mako system being prepped for surgery. Credit: UHCW NHS Trust

Mako robotic system assisted surgery. Credit: UHCW NHS Trust

COI Statement

JM, SF, DD, and DE report funding from the UK National Institute for Health and Care Research (NIHR) for this study. AM reports a NIHR grant to institution and Stryker benefit in kind for this study; is chief or co-investigator on two other studies with NIHR grants to institution and Stryker benefit in kind; reports further NIHR grants; has received payment for expert testimony for the UK COVID Inquiry; is Director and Chief Medical Officer of VerIQ; is Secretary for the British Patellofemoral Society; was research lead of the British Association of Surgery for the Knee; is on a clinical advisory board for Sagence; and holds stock in VerIQ and Sagence. AT reports research grants from Stryker Masters Services Framework research agreement, NIHR, and Versus Arthritis; royalties from Corin; and consulting fees and payment for presentations from Stryker, Corin, Adler, and Quadsense. CS reports research grants from Stryker; consulting fees from Stryker, Smith & Nephew, and Osstec; payment for lectures from Zimmer Biomet; was a member of a Data Safety and Monitoring Board and an advisory board for Smith & Nephew; is Editor in Chief for Bone & Joint Research; and is on the editorial board of The Bone & Joint Journal. CK reports a salary from the RACER-Knee grant and Stryker benefit in kind for this study. ED reports an NIHR grant and Stryker excess treatment costs for this study; research funding from Smith & Nephew and Stryker to institution; royalties from Smith & Nephew and Microport; consulting fees from Smith & Nephew, Microport, and Garland Surgical; payment for lectures from Smith & Nephew, Stryker, and Microport; payment as an expert witness for Irwin Fritchie Urquhart Moore & Daniels and Hogan Lovells International; financial support for attending meetings from Smith & Nephew, Stryker, Zimmer Biomet, and Microport; holds shares in VerIQ and Garland Surgical; and is the Director of Precision Joint Replacement. FH reports an NIHR grant for this study; research grants from the NIHR, Stryker, Smith & Nephew, Corin, and the International Olympic Committee; royalties or licenses from Smith & Nephew, Stryker, Corin, MatOrtho, and Springer; consulting fees for Stryker; payments for lectures and presentations from Stryker, Zimmer Biomet, and AO Recon; financial support for travel from Stryker, Zimmer Biomet, AO Recon, and The Bone & Joint Journal; is a member of The Bone & Joint Journal editorial board; is President of the International Hip Society; is President of the European Hip Society; and is an International Society for Technology in Arthroplasty board member. HP reports an NIHR grant to institution and Stryker benefit in kind for this study; research grants from the NIHR; and participated in three independent oversight committees for NIHR-funded studies. MU reports an NIHR grant to institution and Stryker funding to the UK National Health Service for this study; grants from the NIHR, Norwegian Medical Research Council, and Australian National Health and Medical Research Council; royalties from the University of Warwick; accepted travel and accommodation costs as an invited speaker on back pain, at UK scientific meetings from the British Pain Society and the Society for Back Pain Research; participated in a Data Safety and Monitoring Board for the NIHR; is a director at and shareholder in Clinvivo; and declares that Stryker has supplied clinical materials for another ongoing and one completed randomised controlled trial, both funded by the NIHR. NCl reports funding from Stryker for other research grants not related to this manuscript; and is an editorial board member of The Bone & Joint Journal and Bone & Joint Research. All other authors declare no competing interests.

Breaking up of swan families in winter disrupts spring migration

Universiteit van Amsterdam

First Northward Migration of Juveniles in 2022 that Became Orphaned during Midwinter, Compared to Juveniles with No Indication of Altered Family Status — image:
First northward migration of juveniles in 2022 that became orphaned during midwinter (red, n = 10) compared to juveniles with no indication of altered family status (reference group; blue, n = 14). a) migration tracks; b) migratory progress, measured as the distance (km) from the Ouse Washes in the United Kingdom (the location farthest from the breeding grounds reached by any of the birds); dashed transect lines in a indicate 1,000 km progress intervals for comparison. Circles indicate final track locations for individuals that subsequently died in the northern part of the range (four orphans and two from reference group); crosses indicate recorded deaths (two orphans). c) date of crossing 12.5°E, used as a proxy for migration departure. Boxes indicate the inter quartile range (IQR), with the central line depicting the median and the whiskers extending to 1.5*IQR. Fig. created using RStudio (R Core Team 2023) and Inkscape.
view more
Credit: Hans Linssen, University of Amsterdam (Fig. created using RStudio (R Core Team 2023) and Inkscape)

Young Bewick's swans only survive their first spring migration if they stay with their parents long enough. If they lose their parents in winter, they leave later and are unable to keep up with the rest of the population. As a result, there is a greater chance that they will die in their first year of life. This is shown in new research by biologists from the UvA and NIOO-KNAW, together with American and German colleagues, which was published on August 20 in the journal Behavioral Ecology and Sociobiology.

Using GPS transmitters and DNA analysis, Hans Linssen and his colleagues analysed 55 swans – both adult and juvenile – from 12 entire swan families. This gave the researchers insight into family ties, how long families stayed together, and what happened when the bond was broken.

Bewick's swans breed on the Arctic tundra of European Russia, and in the autumn, they fly in family groups to the Netherlands and surrounding countries to spend the winter. Normally, the families stay together until at least halfway through the young's first spring migration back to the north, when the young are nearly one year old. For ten of the 24 young in the study, things turned out differently: they lost their parents during the winter following disturbances at roosting and feeding sites, primarily because hunters invaded a protected nature reserve important to the swans. On average, these orphaned swans departed for the spring migration nearly a month later than other juvenile swans and were much less likely to survive the following winter. The survival rate of the orphans dropped from 86 percent to 40 percent compared to young that stayed with their parents for the majority of the migration.

‘This poignantly shows that living and learning in a family group is not only useful for the young swans, but literally of vital importance,’ says Linssen.

Disappearing over Latvia
One orphaned swan did not leave northern Germany until April, following the same route as its peers but flying a considerable distance behind them. The last GPS signal was picked up over Latvia; after that, the swan disappeared from all records. For several young orphans, the transmitter signal was never picked up again, indicating that they did not survive the summer.

Linssen: ‘There is no telephone network in the swans’ breeding area. As a result, the GPS transmitters cannot send their locations for months. So, during that period, we do not know how the swans are doing. We only receive signals again when they migrate south in October and we regain coverage. Then we see which animals survived the summer. Unfortunately, for most of the orphaned young, such a signal failed to arrive.’

Orphan swan in a foster family
One of the young swans in the study, 036T, presented a more hopeful story. The swan’s mother was shot by hunters at their wintering grounds. In February, 036T left for Great Britain, where she joined another family. For two weeks, the young swan travelled with this family across British fields and later towards northern Germany, until the bond was broken in mid-March. On 26 March, 036T began the spring migration independently, somewhat on the late side. Then, in September, she met her biological father again in the Russian Arctic. They subsequently travelled south together for another week. Five years later, 036T is still alive.

Declining population
The findings are particularly concerning because the population of Bewick's swans in northwest Europe has been declining for years. Increased mortality among young birds can only exacerbate this decline. The study emphasises that protecting the birds is not just about nature reserves where they can live, but also about peace and quiet during the winter and the first spring migration. Linssen: 'It is crucial for young swans to be able to spend at least their first winter and spring migration with their family. Disturbances during that vulnerable period can have fatal consequences, so we must keep them to a minimum.'

About the Bewick's Swan
The Bewick's Swan is the smallest of three swan species found in the Netherlands and Belgium. Bewick's swans breed on the coast of European Russia and overwinter in northwest Europe. In the past, this was mainly in England and the Netherlands, but now it has largely shifted to northwest Germany. For migratory birds, timing is crucial: if they arrive too late at the breeding site, they miss the peak in food availability and their breeding success declines.