Is Robotic Surgery Better for Hip and Knee Replacement?

What is robotic surgery in joint replacement?

Robotic joint replacement — most commonly associated with the Mako system (Stryker) or ROSA (Zimmer Biomet) — is not fully autonomous surgery. The robot does not operate independently. Instead, it is a surgeon-controlled assistive tool that provides three main functions:

• A pre-operative CT scan is used to create a three-dimensional model of your specific anatomy and plan the implant position
• Intraoperative software displays your anatomy in real time and shows the surgeon exactly where the implant will be positioned
• A robotic arm provides haptic feedback and, in some systems, limits the cutting instrument to a pre-planned zone to reduce the chance of moving outside intended boundaries

The goal is consistent, accurate implant alignment — the same goal that underpins every joint replacement technique, whether robotic, computer-assisted, or manual. The robot is a tool to achieve that goal; it does not replace surgical skill, decision-making, or technique.

What the evidence actually shows

The research on robotic joint replacement has expanded substantially over recent years, and the picture is now clearer — though more nuanced than most marketing suggests. The most rigorous data comes from randomised controlled trials (RCTs) and large registry studies, including the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR).

For hip replacement, a 2024 systematic review and meta-analysis of 8 RCTs involving 1,014 patients — published in the Journal of Robotic Surgery — found no difference in revision rates between robotic-assisted and conventional hip replacement (relative risk 1.33; 95% CI 0.08–22.74), no difference in major complication rates, and no significant difference in patient-reported outcome measures. Robotic surgery did demonstrate superior accuracy in implant placement, but that technical precision did not translate into measurable clinical benefit at follow-up.

For knee replacement, a 2024 RCT published in The Bone and Joint Journal (Clement et al.) found no significant difference in functional outcomes between robotic arm-assisted and conventional total knee replacement. A separate meta-analysis found improved Forgotten Joint Scores (a measure of how naturally a patient's joint feels after surgery) at one, two, and five years for robotic-assisted knees. However, the same analysis noted that robotic surgery adds an average of 32.9 minutes to operative time — a factor that carries its own considerations for anaesthetic duration and surgical risk.

The headline finding across the highest-quality evidence is consistent: robotic surgery may improve alignment precision and may offer modest gains in certain patient-reported measures, but does not reduce revision rates or produce meaningfully superior functional outcomes compared to expert conventional technique. A 2025 umbrella review in the Journal of Clinical Medicine asked directly whether robotic assistance improves outcomes beyond alignment — and concluded that the evidence for clinically meaningful benefit beyond technical accuracy remains limited.

Where robotic surgery does show consistent advantages is in narrowing the variability in implant positioning across a broad population of surgeons — which is precisely why it is most valuable for less experienced surgeons or complex anatomy, and less necessary in high-volume, experienced hands.

Where robotic surgery genuinely adds value

Being evidence-based means acknowledging where robotic surgery does offer real advantages. There are situations where the technology is genuinely beneficial:

• Less experienced surgeons: Robotic assistance narrows the variability in implant alignment across a wider population of surgeons. For a surgeon still developing precision, the technology provides a valuable safety net.
• Complex anatomy: Patients with significant bony deformity, prior implants, unusual anatomy, or severe bone loss can benefit from the three-dimensional pre-operative planning that robotic systems provide.
• Partial (unicompartmental) knee replacement: Some studies suggest the precise bone preparation required for unicompartmental implants may benefit more from robotic assistance than total knee replacement.
• Teaching environments: Robotic systems can assist in training, providing a more controlled environment for surgeons learning joint replacement technique.

The key point is that robotic surgery adds the most value when it compensates for reduced precision. In high-volume, experienced hands, that compensation is less necessary because the precision is already there.

What I use — and why

I do not currently perform robotic-assisted joint replacement. This is a deliberate choice grounded in the evidence and in my own surgical philosophy.

My approach to precision centres on patient-specific technology as a pre-navigation system — meaning the critical work of planning and preparation happens weeks before you ever enter the operating theatre. This is a meaningful distinction. Robotic surgery handles its planning intraoperatively, on the day of surgery. My process works the other way around: by the time surgery begins, every decision about implant sizing, positioning, alignment, and surgical approach has already been made, verified, and locked in.

Using your CT scan and X-rays, I build a three-dimensional model of your joint weeks in advance. I plan the exact implant size, the precise angles of placement, and the specific bone cuts required for your anatomy — not a generic anatomy, yours. Custom cutting guides are then manufactured to those exact specifications. These patient-specific instruments are designed to fit your bone and only your bone, guiding each cut to match the pre-operative plan with a high degree of accuracy.

The result is that on the day of surgery, I am not navigating in real time or relying on intraoperative software to tell me where to cut. I already know. The planning is complete. The operating theatre is where the plan is executed — not where it is made.

For hip replacement, I use the direct anterior approach — a muscle-sparing technique that does not require cutting through the major muscles around the hip. This approach is associated with earlier mobilisation and a more predictable recovery pathway.

Over years of high-volume joint replacement practice, the consistency and precision I achieve through this pre-navigation approach produces the outcomes my patients experience. The evidence supports that this methodology, in experienced hands, is equivalent to robotic-assisted surgery — with the advantage that the preparation work is thorough, unhurried, and completed well before surgery day.

What actually determines your outcome

The most important determinants of a good joint replacement outcome are not the presence or absence of a robotic arm. They are:

• Surgeon experience and procedure volume: High-volume surgeons with years of consistent practice produce more predictable outcomes. This is one of the most replicated findings in the joint replacement literature.
• Patient factors: BMI, general health, bone quality, and how far your joint disease has progressed all influence your individual outcome. These factors matter more than any single surgical technology.
• Implant selection: The choice of implant system and bearing surfaces, matched to your specific anatomy, age, and activity level, is a significant determinant of longevity.
• Rehabilitation: How well you engage with your post-operative physiotherapy and recovery programme determines much of your functional outcome.
• The right procedure at the right time: Having surgery when the clinical indication is clear — not too early, not too late — produces the best results.

When patients ask about robotic surgery, the more useful question to ask any surgeon is: "How many of these procedures have you performed, and what is your revision rate?" The answers to those questions tell you far more about your likely outcome than the presence of a robotic system.

Questions to ask your surgeon

Whether you are consulting with a surgeon who uses robotic assistance or one who does not, the following questions will help you evaluate their experience and approach:

• How many joint replacements do you perform each year, and how many have you performed in total?
• What technique do you use to ensure accurate implant alignment?
• What implant system do you use, and why is it appropriate for me?
• What is your personal revision rate, and how does it compare to the national average in the AOANJRR?
• What does my pre-operative planning involve, and will you show me the plan before surgery?
• What approach do you use for hip replacement, and what are the rehabilitation implications?

A surgeon who can answer these questions clearly and specifically, with data to support their answers, is likely to produce a good outcome regardless of whether they use robotic technology.

Frequently asked questions