Key Takeaways
- A new 2026 meta-analysis comparing functional alignment with mechanical alignment in robotic primary total knee arthroplasty suggests that functional alignment can reduce the need for soft-tissue releases and may improve some early recovery measures, but it has not established a clear long-term functional advantage.
- The larger RASKAL randomised trial provides an important counterweight: despite fewer soft-tissue releases with functional alignment, two-year clinical outcomes were not significantly superior to mechanical alignment.
- Robotic technology makes alignment strategies more measurable and reproducible, but it does not prove that one alignment philosophy is universally best for every patient.
- The clinically relevant question is not simply ‘functional or mechanical alignment?’ but whether the chosen target respects individual anatomy while remaining within safe boundaries and producing a stable, balanced knee.
- Patients should be cautious about marketing claims that present personalised or functional alignment as automatically producing a more natural-feeling or longer-lasting knee.
Introduction
Postoperative AP radiograph following total knee replacement, illustrating implant position.
Total knee arthroplasty has traditionally been performed using mechanical alignment, with the femoral and tibial components positioned according to standardised mechanical-axis targets. This approach has a long clinical history and excellent survivorship, but it intentionally brings very different native knees towards a common alignment goal.
The development of robotic-assisted knee replacement has made alternative alignment philosophies easier to plan and execute with precision. One of these is functional alignment, in which component position is adjusted within defined limits to better respect a patient’s pre-arthritic or constitutional anatomy, soft-tissue behaviour and joint-line orientation. The attraction is understandable: if two patients started with different anatomy, should both necessarily receive exactly the same alignment target?
A new open-access meta-analysis published in SICOT-J on 1 September 2026 compares functional alignment with mechanical alignment specifically in robotic primary total knee arthroplasty (Jamaleddine et al., 2026). The study is timely because personalised alignment is increasingly discussed as the next step after robotic precision. However, the important question is not whether robotics can execute a personalised plan. It can. The question is whether changing the alignment philosophy produces a clinically meaningful advantage for patients.
What the New Meta-analysis Adds
The 2026 meta-analysis pooled the available comparative robotic literature on functional versus mechanical alignment. Across the included studies, functional alignment was associated with less need for soft-tissue release and showed advantages in some early outcome measures (Jamaleddine et al., 2026). This finding is biologically plausible. If implant position is adjusted to better accommodate the patient’s native joint line and soft-tissue envelope, the surgeon may need fewer ligament releases to achieve balance.
That is an important technical observation because soft-tissue release is not a trivial step. Ligaments influence stability, proprioception, and knee kinematics. Avoiding an unnecessary release may preserve the patient’s native envelope and can simplify balancing. Robotic systems are particularly suited to this strategy because they can quantify gaps, model the consequences of small component-position changes and help the surgeon test a plan before bone cuts are completed.
However, the meta-analysis does not support the stronger conclusion that functional alignment has already been proven superior. By around one year, the functional differences were not consistently superior across outcomes (Jamaleddine et al., 2026). The included studies also varied in design, robotic platform, exact definition of functional alignment, safe boundaries, implant type, rehabilitation pathway and surgeon experience. Those differences matter when combining results.
Why the RASKAL Trial Matters
The new meta-analysis should be interpreted alongside the RASKAL randomised controlled trial, which compared functional and mechanical alignment in robotic total knee arthroplasty in a substantially larger prospective cohort (MacDessi et al., 2026). Randomisation is particularly valuable here because alignment philosophy can otherwise become entangled with surgeon preference, patient selection and different peri-operative pathways.
RASKAL similarly found that functional alignment substantially reduced the need for soft-tissue releases (MacDessi et al., 2026). That reinforces the technical signal seen in the new meta-analysis: robotic planning can often achieve balance by adjusting component position within safe limits rather than automatically releasing ligaments to make the knee conform to a fixed mechanical target.
But the RASKAL trial did not demonstrate a significant two-year clinical superiority of functional alignment (MacDessi et al., 2026). Pain, function and patient-reported recovery were not transformed simply because fewer releases were required. This is a useful reminder that a technically elegant intra-operative strategy does not automatically translate into a large difference that every patient can feel.
The two studies therefore tell a coherent story rather than a contradictory one. Functional alignment appears capable of changing how the operation is executed, particularly in relation to balancing and soft-tissue release. What remains less certain is how much that technical difference improves medium- and long-term patient-reported outcomes, satisfaction, complications or implant survival.
Mechanical Alignment Is Not ‘Wrong’
Discussion of personalised alignment can sometimes imply that mechanical alignment is outdated. That would be an overstatement. Mechanical alignment has decades of clinical experience behind it and remains a reproducible, evidence-based strategy with very good long-term results.
Its strength is standardisation. By targeting a neutral mechanical axis, it provides clear reference points and avoids extreme component positions. The potential limitation is that native knee anatomy is not identical across the population. Some patients naturally have constitutional varus or valgus alignment, and restoring every knee to the same neutral target may alter the relationship between bone geometry and soft tissues.
Functional alignment tries to address that limitation, but it should not be interpreted as unrestricted restoration of native deformity. A severely arthritic knee may have acquired deformity rather than healthy constitutional alignment. The surgeon still needs to distinguish pre-arthritic anatomy from pathological change and to keep implant position within safe boundaries.
What Robotics Changes – and What It Does Not
Robotic assistance has changed the alignment debate because it gives the surgeon more reliable measurements. The system can register patient anatomy, quantify alignment, assess medial and lateral gaps through the range of motion and model how small changes in component position affect balance. That makes patient-specific planning more practical than when surgeons relied mainly on standard cutting guides and subjective assessment.
But robotics does not decide the target. It accurately helps execute the strategy chosen by the surgeon. If the planned alignment target is inappropriate, achieving it with sub-millimetre precision does not make the plan correct. Precision and judgement remain separate concepts.
The same distinction applies to recovery. Robotic alignment is only one component of total knee replacement. Surgical approach, tissue handling, anaesthesia, pain control, blood management, muscle preservation, physiotherapy, pre-operative function, medical comorbidities and patient expectations all influence early recovery. A particular alignment philosophy should therefore not be marketed as a stand-alone explanation for faster walking or a more ‘natural’ knee.
My Clinical Interpretation
For a practising joint-replacement surgeon, the most useful message from these studies is not that every robotic knee should now be functionally aligned. It is that robotics gives us the ability to individualise within boundaries and to reduce unnecessary soft-tissue disruption when the anatomy allows it.
In one patient, a mechanically aligned plan may already produce acceptable gaps and component positions without extensive release. In another, a modest adjustment of femoral or tibial position may achieve balance while respecting the patient’s anatomy more closely. The value of the robotic platform is that these options can be measured rather than guessed.
Patient selection also matters. Severe fixed deformity, bone loss, ligament incompetence, previous surgery or unusual anatomy may limit how far a personalised plan can safely move from conventional targets. Alignment philosophy should therefore remain a surgeon-led decision based on anatomy, stability, implant constraints and the clinical objective rather than a label selected before the knee has been assessed.
What Should Patients Ask?
Patients do not need to choose an alignment philosophy from an advertisement. A more useful consultation asks: What is my native anatomy likely to have been? How much of my present alignment represents arthritis-related deformity? Which alignment strategy is being proposed, and why? Will the robotic system be used to measure balance through the range of motion? Are there safe limits beyond which the plan will not be adjusted? What evidence supports the expected benefit in a patient like me?
The surgeon should also be able to explain what cannot be promised. Functional alignment may reduce ligament releases and may produce early benefits in selected patients, but current evidence does not justify guaranteeing a more natural-feeling knee, faster recovery for everyone or superior implant longevity.
Final Thoughts
The new 2026 meta-analysis strengthens an important technical argument for functional alignment in robotic knee replacement: when component position is individualised within safe limits, surgeons may be able to achieve balance with fewer soft-tissue releases. The RASKAL randomised trial supports the same technical observation (Jamaleddine et al., 2026; MacDessi et al., 2026).
At the same time, both bodies of evidence caution against overinterpretation. Fewer releases are not the same as proven long-term clinical superiority. At present, the evidence supports functional alignment as a credible, increasingly measurable strategy – not as a universal replacement for mechanical alignment.
The broader lesson is that robotic surgery should move the discussion beyond simply asking whether a robot is used. The more meaningful questions are what plan is being executed, why that plan suits the individual knee, what boundaries are being respected, and how the surgeon integrates technology with clinical judgement. Precision is valuable. Personalisation may be valuable. But neither should be separated from evidence.
Frequently Asked Questions
Is functional alignment the same as robotic knee replacement?
No. Functional alignment is an alignment philosophy. Robotic assistance is a technology that can help the surgeon measure, plan and execute that philosophy more precisely.
Is functional alignment proven better than mechanical alignment?
Not conclusively. Current studies show a consistent reduction in soft-tissue releases and some early advantages, but larger randomised evidence has not shown clear two-year clinical superiority (Jamaleddine et al., 2026; MacDessi et al., 2026).
Does functional alignment mean leaving the knee in its original deformity?
No. The aim is to respect constitutional anatomy within defined safe limits, not to reproduce pathological deformity caused by advanced arthritis.
Can functional alignment make the knee feel more natural?
That is one of the proposed advantages, but current evidence does not support guaranteeing a more natural-feeling knee for every patient.
Does the robot choose whether I receive functional or mechanical alignment?
No. The surgeon selects the alignment strategy. The robotic system assists with measurements, planning and execution.
Does fewer ligament release mean faster recovery?
It may contribute to tissue preservation, but recovery is multifactorial. Surgical approach, pain control, muscle function, rehabilitation, health status and several other factors also matter.
References
Jamaleddine, Y., Maroun, R., Assi, C., Khoury, A., & Kouyoumdjian, P. (2026). Functional versus mechanical alignment in robotic primary total knee arthroplasty: A meta-analysis. SICOT-J, 12, 50. https://doi.org/10.1051/sicotj/2026061
MacDessi, S. J., Wernecke, G. C., Ghadirinejad, K., Wood, J. A., Holder, C., Lorimer, M., Harris, I. A., Bastiras, D., Boyle, R., Chen, D. B., Du, P., Fritsch, B., Guzman, M., Kirsh, G., Leong, A., Limbers, J., McEwen, P., McMahon, S., Mulford, J., . . . Yu, J. (2026). Robotic-assisted surgery and functional alignment in total knee arthroplasty: The RASKAL registry-nested 2 × 2 factorial randomized trial. The Bone & Joint Journal, 108-B, 622–633. https://pubmed.ncbi.nlm.nih.gov/41944850/
