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Knee Replacement Explained
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All topics
  1. What it is
  2. Who it helps
  3. Timing
  4. The procedure
  5. Before and after surgery
  6. Recovery supplies
  7. Implant designs
  8. Side-by-side
  9. Robotics and alignment
  10. Robotic systems
  11. US manufacturers
  12. What the evidence says
  13. Value analysis
  14. Finding a surgeon
  15. Insurance and costs
  16. Questions to ask
  17. Resources
  18. Glossary
  19. References

Technology

Robotic knee systems: Mako, CORI, ROSA and VELYS

Four robotic systems account for most robotic-assisted knee replacements in the US. Each is made by a major implant company, and each works only with that company’s own knee implants. So the robot your surgeon uses usually goes hand in hand with the implant they prefer.

In every case the surgeon still does the operation. The robot helps plan the bone cuts and keeps them on target. For how robotic surgery works in general, and what the research shows, see Robotics and alignment.

Systems are listed in the order they first reached the US market for knee surgery. This is not a ranking. Descriptions of features come from each company and from industry press, and are labeled that way.

How long each system has been around

Key US milestones, 2004 to 2026

Scroll sideways to see the full timeline.

Robotic knee systems timelineTimeline of the four robotic knee systems from 2004 to 2026. Mako: 2006 First partial knee case; 2013 Stryker buys MAKO; 2015 Total knee cleared; 2025 Mako 4. CORI: 2012 NAVIO cleared; 2016 S+N buys Blue Belt; 2020 CORI cleared; 2026 Cementless knee. ROSA: 2016 ZB buys Medtech; 2019 ROSA Knee cleared; 2021 Partial knee; 2025 OptimiZe. VELYS: 2018 J&J buys Orthotaxy; 2021 VELYS cleared; 2024 Partial knee.200420062008201020122014201620182020202220242026MakoStryker2006 First partial knee case2013 Stryker buys MAKO2015 Total knee cleared2025 Mako 4CORISmith+Nephew2012 NAVIO cleared2016 S+N buys Blue Belt2020 CORI cleared2026 Cementless kneeROSAZimmer Biomet2016 ZB buys Medtech2019 ROSA Knee cleared2021 Partial knee2025 OptimiZeVELYSDePuy Synthes2018 J&J buys Orthotaxy2021 VELYS cleared2024 Partial knee
Dates from company announcements, FDA records and industry press listed under Sources. Clearance means FDA 510(k) clearance in the US.

Years on the US market for knees

Scroll sideways to see the full table.

SystemFirst US knee useTotal knee clearedYears of total knee use (2026)
Mako (Stryker)2006 (partial knee)201511
CORI / NAVIO (Smith+Nephew)2012 (NAVIO partial knee)2017 (NAVIO); CORI 20209 (NAVIO) / 6 (CORI)
ROSA (Zimmer Biomet)2019 (total knee)20197
VELYS (DePuy Synthes)2021 (total knee)20215

The four systems

Mako

Stryker

The longest history of the four in knee surgery, with partial knee cases since 2006.

What the maker says it offers

  • Builds a 3D plan for each patient from a CT scan taken before surgery.5,6
  • A robotic arm holds the saw and keeps each cut inside the planned boundaries, while the surgeon guides it.6
  • Used for total knee, partial knee and hip replacement, with Stryker’s own implants, such as the Triathlon knee.3,4

Keep in mind: Needs a CT scan before surgery, which means an extra imaging appointment and some radiation exposure.

Timeline

  1. 2005MAKO Surgical, founded in 2004, gets FDA clearance for its first robotic guidance system.1
  2. 2006First MAKOplasty partial knee replacement performed.1
  3. 2008Second-generation RIO robotic arm cleared by the FDA.2
  4. 2013Stryker acquires MAKO Surgical for about $1.65 billion.3
  5. 2015FDA clears the Mako total knee application.3
  6. 2017Full commercial launch for total knee replacement.4
  7. 2025Fourth-generation Mako 4 launched, with spine and shoulder applications added.5

CORI

Smith+Nephew

Handheld robotics in knee surgery since 2012 (NAVIO); CORI itself since 2020.

What the maker says it offers

  • A handheld robotic tool: the cutting burr automatically stops if it moves outside the area mapped in the plan.10
  • No CT scan needed. The knee is mapped during surgery.7,9
  • Compact and portable, which the company says suits outpatient surgery centers.10

Keep in mind: Works with Smith+Nephew implants. The handheld design relies more on the surgeon’s hand than a fixed arm does.

Timeline

  1. 2012Blue Belt Technologies’ NAVIO handheld system cleared for partial knee replacement.7
  2. 2016Smith+Nephew acquires Blue Belt for about $275 million.6
  3. 2017NAVIO adds a total knee application.6
  4. 2020CORI, the next-generation system, cleared by the FDA and launched in the US for total and partial knee replacement.8,9
  5. 2021CORI launched globally.10
  6. 2026FDA clears a cementless version of Smith+Nephew’s LANDMARK knee, designed to work with CORI.11

ROSA

Zimmer Biomet

Used for total knees since 2019.

What the maker says it offers

  • Can build a 3D model from standard X-rays using Zimmer Biomet’s X-Atlas method, or work from measurements taken during surgery.13
  • Gives real-time data on the soft tissues and the balance of the knee as it bends and straightens.12,13
  • The robotic arm positions the cutting guide; the surgeon makes the cuts. Used with Zimmer Biomet’s Persona knee.12,16
  • OptimiZe adds automatic planning for functional or kinematic alignment, based on the surgeon’s preferences.15,16

Keep in mind: Works with Zimmer Biomet implants. The newest planning features were only starting to roll out in 2026.

Timeline

  1. 2010The original ROSA robotic device, made by French company Medtech, cleared for neurosurgery.12
  2. 2016Zimmer Biomet acquires Medtech.12,13
  3. 2019ROSA Knee cleared by the FDA for total knee replacement (January).12
  4. 2021ROSA Partial Knee System cleared (April).14
  5. 2025ROSA Knee with OptimiZe cleared, with automated alignment planning; US rollout planned for early 2026.15,16

VELYS

DePuy Synthes (Johnson & Johnson MedTech)

Used for total knees since 2021.

What the maker says it offers

  • Mounts directly on the side rail of the operating table, giving it a small footprint.18,22
  • No CT, MRI or X-ray needed before surgery. The knee is mapped during the operation.18,22
  • Shows predicted gap balance before bone cuts are made. Used with DePuy Synthes’ ATTUNE knee, and the SIGMA HP partial knee.18,19

Keep in mind: Works with DePuy Synthes implants. It is the newest of the four, so it has the shortest track record.

Timeline

  1. 2018Johnson & Johnson acquires Orthotaxy, the developer behind VELYS.17
  2. 2021FDA clears the VELYS Robotic-Assisted Solution for total knee replacement (January 14).18
  3. 2024VELYS cleared for partial knee replacement (June).19

What the evidence shows

The features above describe what each system is designed to do. Whether they make patients feel better is a separate question.

  • In the RACER-Knee trial, published in 2026, 339 patients were randomly assigned to Mako or to conventional surgery. The robot placed implants more precisely, but patients reported no meaningful difference in how their knee felt at one year.20
  • A 2026 review of randomized trials found no difference in pain, function or satisfaction between robotic and conventional knee replacement, with longer operating times for robotic cases.21
  • Head-to-head trials comparing these four systems with each other are rare, so there is no good evidence that one system leads to better results than another.

Your surgeon’s experience with whichever system they use, and with knee replacement overall, is likely to matter more than the brand of robot. More on this in The future of knee replacement technology.

Questions to ask about robotic surgery

  • Which robotic system do you use, and how many robotic knee replacements have you done with it?
  • Will I need a CT scan or special X-rays before surgery?
  • Does using the robot change which implant I get?
  • Does it change the cost to me, the length of surgery or my recovery plan?
  • What would you do differently if we didn’t use the robot?

See all of our questions to ask your surgeon.

Sources for this page

  1. MAKO comes out with RIO system, Restoris implants. Medical Device Daily / BioWorld. 2009. bioworld.com
  2. MAKO Surgical Corp. Receives FDA clearance to market Version 2.0 Tactile Guidance System (RIO). Press release. December 2, 2008. biospace.com
  3. Stryker gets FDA nod to use Mako robot for total knee reconstruction. Fierce Biotech. August 2015. fiercebiotech.com
  4. Stryker launches Mako total knee application. ORTHOWORLD. 2017. orthoworld.com
  5. Stryker showcases next generation of Mako SmartRobotics at AAOS 2025 Annual Meeting. Press release. March 11, 2025. stryker.com
  6. Surgical robots: why Stryker’s Mako is driving knee replacement growth. The Robot Report. 2019. therobotreport.com
  7. U.S. robot surgery market gets a new player with FDA nod for Blue Belt Technologies. MassDevice. December 11, 2012. massdevice.com
  8. FDA 510(k) clearances for Blue Belt Technologies, including Real Intelligence CORI (K193120, February 14, 2020). 510kdatabase.net
  9. Smith+Nephew launches Real Intelligence and CORI Surgical System. Press release. July 14, 2020. smith-nephew.com
  10. Smith+Nephew expands reach of its CORI handheld robotic system. MassDevice. November 24, 2021. massdevice.com
  11. Smith+Nephew Third Quarter 2026 Trading Update. November 4, 2026. investegate.co.uk
  12. FDA clears Zimmer Biomet’s ROSA Knee. Ryan Orthopaedics (OTW). January 2019. ryortho.com
  13. Zimmer Biomet receives FDA clearance for ROSA Knee System for robotically-assisted surgeries. Press release via DotMed. January 2019. dotmed.com
  14. Zimmer Biomet receives FDA clearance for ROSA Partial Knee System. Press release. April 20, 2021. investor.zimmerbiomet.com
  15. Zimmer Biomet receives U.S. FDA clearance for enhanced version of ROSA Knee robotic technology (ROSA Knee with OptimiZe). Press release. November 14, 2025. investor.zimmerbiomet.com
  16. FDA clears Zimmer Biomet’s updated knee robotic technology. Medical Design & Development. November 2025. medicaldesigndevelopment.com
  17. J&J wins clearance for VELYS Robotic-Assisted Solution. MD+DI. January 22, 2021. mddionline.com
  18. DePuy receives clearance for ortho robotic system (VELYS, cleared January 14, 2021). Ryan Orthopaedics (OTW). January 2021. ryortho.com
  19. DePuy Synthes Velys earns FDA nod for partial knee replacements. Becker’s Spine Review. June 2024. beckersspine.com
  20. Parsons H, Metcalfe A, Griffin J, et al. Robotic-arm-assisted versus conventional total knee replacement (RACER-Knee): a randomised controlled trial. Lancet. 2026. doi:10.1016/S0140-6736(26)00986-4
  21. Abdelaziz O, et al. Comparative pain relief and functional outcomes following robotic-assisted versus conventional total knee arthroplasty: a GRADE-assessed meta-analysis with meta-regression of randomized controlled trials. J Robot Surg. 2026;20(1). doi:10.1007/s11701-026-03934-0
  22. DePuy Synthes earns FDA clearance for knee-replacement robotic-assistance platform. FDAnews. January 22, 2021. fdanews.com