CORI vs Mako: How Robotic Knee Replacement Systems Compare

When patients in my clinic ask about robotic knee replacement, the conversation often turns into a brand contest. "Is the Mako better than the CORI?" "Which robot should I choose?" It is a fair question, and the honest answer surprises people: the two systems are built differently, but neither has been shown to give you a better knee than the other.

I am Dr. Vishnu Baburaj, consultant orthopaedic surgeon at Aster MIMS Hospital, Kannur (MS Orthopaedics, PGIMER Chandigarh; MRCS, UK). I use the Smith and Nephew CORI system here in North Kerala. In this article I want to compare CORI and Mako fairly, explain the genuine design differences, and be clear about what the evidence does and does not say. If you want the bigger picture on robotics first, my guide to robotic knee replacement in Kannur is a good starting point.

The two systems, in one sentence each

CORI, made by Smith and Nephew, is a handheld, image-free robotics-assisted system. It does not need a pre-operative CT scan or MRI. During surgery the surgeon maps the patient's own bone landmarks with a handheld probe, the software builds a 3D model of the knee and checks the gaps through the full range of motion, and the surgeon then removes bone and positions the implant under the system's guidance using a surgeon-controlled handpiece.

Mako, made by Stryker, is a robotic-arm system that is CT-based. It uses a CT scan taken before surgery to build a 3D model and a surgical plan. During the operation a semi-active robotic arm provides haptic, or tactile, boundaries so that the cutting burr stays within the planned area.

Both are trying to solve the same problem: getting the implant into exactly the right position for your individual knee, more consistently than freehand instruments allow.

The real trade-off: imageless versus CT-based

Most of the practical difference between these two systems comes down to one decision the engineers made: whether to plan from a scan taken beforehand, or to map the knee during the operation itself. Each approach has honest pros and cons.

Neither column is "right." A surgeon who values a fully rehearsed pre-operative plan may prefer the CT-based approach. A surgeon and patient who value a simpler pathway, with no scan to arrange and no planning radiation, may prefer image-free. The destination, a precisely placed implant, is the same.

What the evidence actually shows

Here is the part I am most careful about. Across the published trials, robotic-assisted knee replacement reliably improves the accuracy and consistency of implant alignment compared with conventional, freehand instruments. There are fewer alignment outliers, meaning fewer knees that end up further from the target than intended.

One systematic review and meta-analysis of randomised trials found robotic surgery roughly halved the risk of mechanical-alignment outliers compared with conventional technique, while showing little to no difference in patient-reported function scores. Other reviews report the same pattern: better alignment restoration, similar pain, function, satisfaction, complication and revision rates in the short to medium term, and a modestly longer operating time. Some studies also report lower blood loss with robotics.

Crucially, almost all of this evidence compares robotic against conventional surgery. There is no robust head-to-head evidence that CORI produces better outcomes than Mako, or the reverse. When you read a neutral comparative assessment of the current robotic systems, the systems differ in imaging and workflow, not in any proven patient-outcome ranking.

So how should you actually choose?

If the systems are comparable on outcomes, the sensible question is not "which robot," but "which surgeon and which plan for my knee." The implant system, the surgeon's experience with their platform, the hospital's setup, and your own anatomy matter more than the brand on the console.

In my practice at Aster MIMS Kannur I use CORI. I chose an image-free workflow because for most of my patients it is simply a cleaner pathway: there is no separate CT scan to arrange, no additional radiation for the planning step, and nothing extra to schedule before the day of surgery. I map the knee live in theatre and assess the gaps through the full range of motion, and I remain in control of the handpiece throughout. That said, I would not tell a patient that CORI is "better" than Mako. A skilled surgeon using Mako can deliver an excellent result. The technology is a tool, and the right tool in experienced hands is what matters.

If you are weighing up robotic surgery, you can read more about how the procedure works on my robotic knee replacement page, or compare it directly with manual technique in my robotic knee replacement guide. When you are ready to talk through your own knee, you can book a consultation at the clinic.

A note for patients in North Kerala

Robotic-assisted knee replacement is available right here in Kannur. Patients from across the Malabar region, including Thalassery, Payyannur, Taliparamba, Mattannur, and Iritty, no longer need to travel to Kochi or Bangalore to access this technology. What you should look for is not a particular brand of robot, but a surgeon who will plan your surgery carefully, explain the trade-offs honestly, and stand behind your result.