Robotic-arm-assisted versus conventional total knee replacement (RACER-Knee): a pragmatic, multicentre, participant-masked and assessor-masked, superiority, randomised controlled trial
In brief
Robotic-arm knee replacement shows no benefit in joint awareness after 12 months
In a masked, multicentre trial of 339 patients, the Mako robotic system did not improve the Forgotten Joint Score at one year compared with conventional instruments (mean difference -1.5 points, not clinically meaningful). Costs were higher with the robot and serious adverse events were equal, suggesting no patient advantage in routine practice.
- Journal
- Lancet (London, England) (Q1)
- Published
- 20 August 2026
- Study design
- Randomized controlled trial
- Evidence level
- Level 1, High (CEBM 1b)
- Authors
- Helen Parsons, Andrew Metcalfe, James Griffin, Chetan Khatri, Helen Bradley, Mark Blyth, et al.
- PMID
- 42624811
- DOI
- 10.1016/S0140-6736(26)00986-4
Why clinicians should know about it
- Picked for Surgery (top studies of the week, 23 August 2026): Robotic knee trial irrelevant to GI surgery
- Picked for Breast and Endocrine Surgery (top studies of the week, 23 August 2026): Not surgical oncology; orthopedic trial unrelated to breast/endocrine surgery
- Picked for Bariatric and Metabolic Surgery (top studies of the week, 23 August 2026): Ranked by evidence level and journal quartile
- Picked for Orthopedics and Sports Medicine (top studies of the week, 23 August 2026): Superiority RCT, no functional benefit
Abstract
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.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.