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

@article{parsons2026roboticarmassisted,
  title = {{Robotic-arm-assisted versus conventional total knee replacement (RACER-Knee): a pragmatic, multicentre, participant-masked and assessor-masked, superiority, randomised controlled trial}},
  author = {Helen M. Parsons and Andrew John Metcalfe and James Milton Griffin and Chetan Khatri and Helen Bradley and Mark Blyth and Nicholas Clement and Nirvana Croft and David J. Deehan and David Ellard and Samuel N. Frempong and Nicholas Grant and Fares Sami Haddad and Charles E. Hutchinson and James Mason and Hema Mistry and Seyran Naghdi and Chloe Scott and Toby Smith and John Andrew Skinner and Andrew H. Toms and Sophie Rees and Bryan Riemer and Martin R Underwood and E T Davis and David Beard and Paul N. Baker and Stephen McDonnell and Thomas Pinkney and Yemi Oluboyede and Nick Howells and Steve Asplin and Graham Howkins and Mike Reed and Andrew Judge and Graeme MacLennan and Issaq Ahmed and Anish Amin and Christine Beadle and Caroline Blackstock and Paul Gaston and Ewan B. Goudie and Pauline Irvine and Gavin Macpherson and Eliott Sophie Martinson and Shona McDonald and Victoria Minnis and Matthew Moran and Rachel O'Brien and James Patton and Beena Poulose and Phil M.S. Simpson and Frazer A. Wade and James Doonan and Colin Drury and Bryn Jones and Jennifer Miller and Gary Semple and Natasha Grabor and K J Smith},
  journal = {The Lancet},
  year = {2026},
  month = aug,
  doi = {10.1016/s0140-6736(26)00986-4},
  url = {https://doi.org/10.1016/s0140-6736(26)00986-4},
  note = {CC BY},
}

TY  - JOUR
TI  - Robotic-arm-assisted versus conventional total knee replacement (RACER-Knee): a pragmatic, multicentre, participant-masked and assessor-masked, superiority, randomised controlled trial
AU  - Helen M. Parsons
AU  - Andrew John Metcalfe
AU  - James Milton Griffin
AU  - Chetan Khatri
AU  - Helen Bradley
AU  - Mark Blyth
AU  - Nicholas Clement
AU  - Nirvana Croft
AU  - David J. Deehan
AU  - David Ellard
AU  - Samuel N. Frempong
AU  - Nicholas Grant
AU  - Fares Sami Haddad
AU  - Charles E. Hutchinson
AU  - James Mason
AU  - Hema Mistry
AU  - Seyran Naghdi
AU  - Chloe Scott
AU  - Toby Smith
AU  - John Andrew Skinner
AU  - Andrew H. Toms
AU  - Sophie Rees
AU  - Bryan Riemer
AU  - Martin R Underwood
AU  - E T Davis
AU  - David Beard
AU  - Paul N. Baker
AU  - Stephen McDonnell
AU  - Thomas Pinkney
AU  - Yemi Oluboyede
AU  - Nick Howells
AU  - Steve Asplin
AU  - Graham Howkins
AU  - Mike Reed
AU  - Andrew Judge
AU  - Graeme MacLennan
AU  - Issaq Ahmed
AU  - Anish Amin
AU  - Christine Beadle
AU  - Caroline Blackstock
AU  - Paul Gaston
AU  - Ewan B. Goudie
AU  - Pauline Irvine
AU  - Gavin Macpherson
AU  - Eliott Sophie Martinson
AU  - Shona McDonald
AU  - Victoria Minnis
AU  - Matthew Moran
AU  - Rachel O'Brien
AU  - James Patton
AU  - Beena Poulose
AU  - Phil M.S. Simpson
AU  - Frazer A. Wade
AU  - James Doonan
AU  - Colin Drury
AU  - Bryn Jones
AU  - Jennifer Miller
AU  - Gary Semple
AU  - Natasha Grabor
AU  - K J Smith
PY  - 2026
DA  - 2026/08/20
JO  - The Lancet
DO  - 10.1016/s0140-6736(26)00986-4
UR  - https://doi.org/10.1016/s0140-6736(26)00986-4
AB  - BACKGROUND: Robotic systems are being increasingly used to assist with total knee replacement (TKR). Whether robotic systems improve outcomes after TKR is uncertain. We aimed to ascertain the clinical efficacy and cost-effectiveness of the Mako robotic-arm system compared with conventional instruments for TKR. METHODS: We conducted a participant-masked and assessor-masked pragmatic, superiority, randomised controlled trial at ten hospitals in Great Britain involving 33 surgeons. Patients with advanced knee osteoarthritis underwent TKR with conventional instruments (cTKR) or with the Mako robotic-arm-assisted system (rTKR). Key exclusion criteria were inflammatory arthropathy, previous fracture, or the need for complex implants. Participants were randomly assigned (1:1) through a remote computer system using minimisation by age, BMI, centre, surgeon, and primary knee compartment involved. Participants and assessors were masked through methods including using sham incisions, additional draping, and masked operation notes. The primary outcome was the Forgotten Joint Score (FJS) at 12 months after randomisation according to the intention-to-treat principle using a linear mixed-effects model. The prespecified target difference was 12 points. The trial is registered with ISRCTN (ISRCTN27624068), and long-term follow-up is ongoing. FINDINGS: Between Dec 21, 2021, and Dec 13, 2023, 807 patients were screened and 339 were randomly assigned: 168 to rTKR and 171 to cTKR. The median age was 68·8 years (IQR 61·3-75·2), 167 (49%) were female, and 172 (51%) were male. At 12 months, the mean FJS was 49·2 (SD 28·4; n=154) in the rTKR group and 50·2 (29·9; n=158) in the cTKR group. The adjusted mean difference was -1·5 (95% CI -7·5 to 4·5; p=0·62,) favouring cTKR. 16 participants in each group had one serious adverse event. INTERPRETATION: In this pragmatic trial, rTKR as delivered in routine practice was more costly than cTKR and did not provide a clinically meaningful patient benefit at 12 months after randomisation. The two groups had similar safety (ie, harms) profiles. FUNDING: UK National Institute for Health and Care Research Health Technology Assessment Programme.
SN  - 0099-5355
SN  - 0140-6736
SN  - 1474-547X
ER  -