CORI robotic knee replacement offers three key advantages: it needs no CT scan before surgery, it plans and balances the new knee in real time during the operation, and it is the only robotic platform covering partial, total, and revision knee replacement. In 2025 NICE conditionally recommended robotic systems, including CORI, for NHS knee replacement, and CORI was the first robotic platform cleared for revision knee surgery, the most demanding knee operation of all.
What Is the CORI Surgical System?
CORI is a handheld robotic-assisted surgical system developed by Smith+Nephew, a British medical technology company. Unlike large robotic-arm platforms, CORI is a compact, surgeon-held instrument: it maps your knee in three dimensions during surgery, helps your surgeon plan the exact position of the implant, and then guides bone preparation with sub-millimetre accuracy.[5]
Crucially, the surgeon, not the robot, performs your operation. CORI cannot move or cut on its own; it protects the plan by only allowing bone removal within the agreed boundaries. You get robotic precision with an experienced surgeon in full control at every step. Mr Hussain uses CORI as part of his robotic knee replacement practice in Birmingham, alongside his Mako and ROSA certifications.
No CT Scan Required: The Image-Free Advantage
Most robotic systems, including Mako, require a CT scan of your knee before surgery. CORI does not. Instead, it builds a live 3D model of your knee at the start of the operation using a tracked mapping probe.
For you as a patient, image-free surgery means:
- No radiation exposure from a pre-operative CT scan
- No extra hospital visit or scan-related delay before your operation
- A plan based on your knee as it actually is on the day, including the cartilage, which a CT scan cannot show
- Real-time adjustment: your surgeon can fine-tune implant position and ligament balance during surgery rather than being locked to a plan made weeks earlier
CORI vs Mako vs ROSA: Side-by-Side Comparison
All three are respected robotic platforms, and each takes a different approach. An independent comparative review in Bone & Joint Open summarised the main differences:[5]
| Feature | CORI | Mako | ROSA |
|---|---|---|---|
| Manufacturer | Smith+Nephew (UK) | Stryker (USA) | Zimmer Biomet (USA) |
| Pre-operative CT scan | Not required (image-free) | Required | Optional (X-ray based) |
| Design | Handheld, surgeon-controlled | Large robotic arm | Robotic arm |
| Knee procedures | Partial, total and revision | Partial and total | Total |
| FDA-cleared for revision knee | Yes, first robotic platform cleared[7] | No | No |
A balanced view matters here: Mako knee replacement and ROSA knee replacement are excellent options, and studies comparing robotic platforms generally show all of them improve the accuracy of implant positioning. Where CORI stands apart is its image-free workflow, its real-time soft-tissue balancing, and its uniquely broad range: it is the only platform covering partial, total, and revision knee replacement.
What Does the Clinical Evidence Show?
Robotic surgery should be judged on published evidence, not marketing. The research on CORI's image-free handheld approach includes:
- A prospective randomised controlled trial found significantly more accurate implant placement with the image-free handheld robotic system than with conventional instruments, confirmed by post-operative CT assessment.[2]
- A 2025 randomised controlled trial reported better clinical outcomes at one year for image-free handheld robotic-assisted knee replacement compared with conventional surgery, including higher Oxford Knee Scores.[3]
- A randomised trial of 215 patients found robotic-assisted surgery with imageless systems accurately restored femoral rotational alignment with satisfactory clinical outcomes.[4]
- A series of 500 consecutive CORI knee replacements reported a short learning curve of around six cases and no infections or revisions.[6]
A note of balance: some studies show that long-term function after robotic and well-performed conventional knee replacement can be similar. What the evidence consistently shows is that robotics improves the precision and consistency of implant positioning, reducing the risk of the outliers and malalignment associated with early failure, with growing evidence of less early pain and faster early recovery.
Every robotic system makes knee replacement more precise. CORI goes further: it measures your knee as it actually is, in theatre, on the day, and lets the surgeon adjust the plan in real time. No scan, no guesswork, and one platform for every type of knee replacement, from partial to revision.
How Robotic Compares With Conventional Knee Replacement
In conventional knee replacement, bone cuts are made using mechanical jigs and rods, guided by the surgeon's eye and experience. This works well in most hands, but small variations in alignment are common. With CORI, the plan is measured, the ligament balance is checked objectively through the full range of movement, and the bone preparation is robotically constrained to the plan, every time.
For patients, this precision matters because implant alignment and soft-tissue balance are among the strongest surgical factors influencing how natural the knee feels and how long it lasts. You can read how Mr Hussain applies this technology on the CORI robotic knee replacement in Birmingham page.
The First Robotic Platform Cleared for Revision Knee Replacement
Revision surgery, replacing a knee replacement that has worn or failed, is the most technically demanding knee operation. Smith+Nephew was the first orthopaedic company to receive FDA 510(k) clearance for revision knee replacement on a robotic platform, with the first robotic revision cases performed using CORI in 2022.[7]
The image-free approach is particularly valuable in revision surgery: metal implants from the original operation distort CT scans, but CORI maps the joint directly, including bone defects revealed after the old implant is removed. That a system is trusted for the hardest cases says something meaningful about its precision in routine ones.
In June 2026, Mr Hussain performed the Midlands' first CORI robotic revision knee replacement, one of the first in the UK, at the Royal Orthopaedic Hospital Birmingham. The full pathway for failed knee implants is explained on the revision knee replacement page.
Partial, Total and Revision Knee Surgery on One Platform
CORI supports the full spectrum of knee replacement: partial (unicompartmental), total, and revision. NICE estimates that up to 40% of patients needing knee replacement may be suitable for a partial knee, yet only around 12% receive one.[1] Robotic assistance makes partial knee replacement more precise and reproducible, helping suitable patients keep more of their natural knee, while the same platform delivers total knee replacement and robotic revision surgery when that is what the knee needs.
Every knee replacement performed in England and Wales is also recorded in the National Joint Registry (NJR), the world's largest joint replacement database, which independently tracks implant survival and surgeon outcomes.[8] Patients can learn how to read a surgeon's NJR results before choosing who operates on them.
Frequently Asked Questions
Does CORI robotic knee replacement need a CT scan?
No. CORI is an image-free system: it builds a precise 3D model of your knee during the operation itself, so there is no pre-operative CT scan, no radiation exposure, and no extra scan appointment before surgery.
Does the robot perform the operation?
No. Your surgeon performs the operation and remains in control at every stage. CORI is a handheld robotic tool that helps plan the implant position and prepare the bone with sub-millimetre precision; it cannot act on its own.
Is robotic knee replacement approved in the UK?
Yes. In 2025 NICE conditionally recommended robotic systems for knee and hip replacement in the NHS, and CORI is among the approved orthopaedic platforms. Robotic knee replacement is also widely available in UK private hospitals, including in Birmingham.
Is CORI available for partial knee replacement?
Yes. CORI supports partial (unicompartmental), total, and revision knee replacement on a single platform, so the same robotic precision applies whichever operation is right for your knee.
How long does recovery take after CORI robotic knee replacement?
Most patients are walking with support on the day of surgery or the day after. Recovery varies between individuals, but studies of robotic-assisted knee replacement report less early pain and good early function, with a full recovery typically taking around three months.
References
- National Institute for Health and Care Excellence. Cutting-edge robotic surgery gets green light as 11 systems are recommended. NICE, 2025.
- Bollars P, et al. Improved accuracy of implant placement with an imageless handheld robotic system compared to conventional instrumentation in patients undergoing total knee arthroplasty: a prospective randomized controlled trial. Knee Surg Sports Traumatol Arthrosc. 2023;31:5446-5452. Full text
- Bollars P, Nathwani D, Albelooshi A, et al. Imageless handheld robotic-assisted total knee arthroplasty showed better clinical outcomes than conventional total knee arthroplasty: a randomized controlled trial with preliminary results at 1-year follow up. The Knee. 2025;56:232-240. PubMed
- Adamska O, et al. Robotic-assisted total knee arthroplasty utilizing NAVIO, CORI imageless systems and manual TKA accurately restore femoral rotational alignment and yield satisfactory clinical outcomes: a randomized controlled trial. Medicina (Kaunas). 2023;59(2):236. Full text
- Comparative assessment of current robotic-assisted systems in primary total knee arthroplasty. Bone & Joint Open. 2023. Full text
- Bagaria V, et al. Complications and learning curve associated with an imageless burr-based (CORI) robotic-assisted total knee arthroplasty system: results from first 500 cases. 2024. PubMed
- Smith+Nephew. Smith+Nephew first to market with revision knee indication on robotics platform. 2022.
- National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. njrcentre.org.uk
This page is for general information and is not a substitute for a consultation. Suitability for robotic-assisted knee replacement is assessed individually.
Mr Shakir Hussain
Consultant Hip and Knee Surgeon at the Royal Orthopaedic Hospital Birmingham. One of a small number of UK surgeons certified on all three major robotic knee platforms: MAKO, ROSA, and CORI.