ROSA: a technical family profile

In brief

• ROSA is a family of separate Zimmer Biomet products, not one universal system.
• ROSA Knee supports imageless and image-based workflows; mandatory CT is not part of either description.
• In the knee workflow, the arm positions a cutting guide and the surgeon makes the saw cut.
• Findings from ROSA Knee, Partial Knee and Hip cannot be pooled.

Three applications

ROSA Knee addresses TKA. ROSA Partial Knee is a separate partial-knee application with its own compatibility. ROSA Hip uses a distinct fluoroscopy-based, CT-free workflow for a direct anterior approach. A shared family name does not make their inputs, instruments or evidence equivalent.

ROSA Knee offers image-based planning using compatible calibrated radiographic data and imageless planning based on landmarks registered in theatre. “Image-based” here does not mean MAKO-style CT-based planning. Partial Knee regulatory materials separately mention compatible X-ray or MRI technologies.

Planning and the cutting guide

After landmark registration, the platform tracks anatomy, supports medial and lateral gap assessment and displays component planning. The clinician changes parameters in response to geometry and soft-tissue balance. The arm positions a cutting guide; the surgeon then passes a conventional saw through it.

The arm therefore does not autonomously cut bone. The clinician owns registration, plan approval, tissue protection, saw movement, cut verification and any change of technique.

Typical ROSA Knee sequence

1. Establish indication and select image-based or imageless workflow.
2. Place optical references and register landmarks.
3. Create or refine the plan.
4. Assess position, motion and joint gaps.
5. Position the guide with the robotic arm.
6. The surgeon cuts and verifies the result.

Evidence

Why the workflow label matters

Imageless ROSA Knee constructs its plan from landmarks registered directly in theatre. The image-based option uses a compatible preoperative reconstruction based on calibrated radiographs. These inputs differ in timing and model generation. Neither should be described as CT-based without qualification.

Workflow selection changes preparation, checkpoints and the interpretation of potential error. Complete registration and stable references are central to imageless cases. Image-based cases add verification of preoperative data and model correspondence. In both, the surgeon must reconcile the display with actual anatomy.

Function of the arm

The ROSA Knee arm positions a guide relative to registered anatomy. It neither carries a cutting instrument inside a haptic volume nor drives a saw autonomously. Once positioned, the clinician fixes and uses the guide while controlling a conventional saw. A generic “robotic arm: yes” field therefore does not make ROSA functionally equivalent to MAKO, CUVIS-joint or VELYS.

Planning supports assessment of component position and joint gaps. Acceptable targets depend on clinical strategy. The platform displays the consequences of parameter changes but cannot select a universally correct answer.

Keeping evidence separate

Any citation should name ROSA Knee or Partial Knee, image-based or imageless mode, software version, implant and study design. Radiographic accuracy in an early series does not establish less pain or fewer revisions. A two-platform study performed by different surgeons may inform a narrow metric while retaining operator and learning-curve effects. ROSA Hip uses a different fluoroscopy-based process; hip and knee findings cannot be exchanged.

A retrospective study compared the first 71 imageless ROSA TKAs with 308 conventional TKAs for actual versus planned resections. It reported no robotic outliers beyond ±3° from plan versus 24% in the conventional group. This early series is not proof of better PROMs or implant survival.

A direct study of the first 50 ROSA and first 50 MAKO TKAs performed by two surgeons found no significant difference in selected radiographic parameters. It cannot establish equality of all functions, risks or clinical outcomes.

Limits and questions

Results depend on version, workflow and implant. Registration and trackers must remain stable. Radiograph-based and imageless planning should not be described as the same process. Hip data do not characterise Knee.

Does ROSA operate without CT? ROSA Knee has no mandatory CT and offers image-based and imageless options.

Does the arm make the cut? It positions a guide; the surgeon controls the saw.

Can Knee evidence be applied to Hip? No. These are different applications and procedures.

Technical accuracy cannot guarantee clinical outcome. Indications require individual assessment. Sources reviewed 8 August 2026; scheduled review August 2027. Author: RoboOrthoClub editorial team. Relevant conflicts must be disclosed.