The three-pillar concept for functional knee positioning in robotic total knee arthroplasty

Total knee arthroplasty (TKA) has traditionally relied on standardised alignment targets, yet a relevant proportion of patients continue to report residual symptoms or dissatisfaction despite excellent implant survivorship. Growing recognition of inter-individual variability in knee phenotype, joint line orientation, ligament behaviour and patellofemoral anatomy has challenged the conventional 'one-size-fits-all' paradigm and promoted the development of more personalised strategies. This narrative review summarises the rationale for a more patient-specific approach to TKA and introduces the concept of functional knee positioning (FKPos) through a practical three-pillar framework integrating bone morphology, ligament behaviour and patellofemoral biomechanics. FKPos represents an evolution of functional alignment, moving beyond static coronal alignment towards an integrated, three-dimensional and patient-specific approach to implant positioning. FKPos is based on three interdependent domains, referred to as the three pillars: bone morphology, ligament behaviour and patellofemoral biomechanics. The bone pillar provides the anatomical foundation by restoring native joint line orientation and three-dimensional morphology within safe boundaries. The ligament pillar aims to achieve individualised, reproducible gap balance through implant positioning rather than systematic soft-tissue release. The patellofemoral pillar considers the anterior compartment as a dynamic and measurable component of knee function, with particular attention to trochlear anatomy, anterior offset and intraoperative tracking. CT-based robotic assistance enables accurate preoperative planning, intraoperative quantification of laxity, controlled adjustment of component position and dynamic assessment of patellofemoral tracking. These technological advances have improved the reproducibility of personalised TKA strategies and allow the three pillars to be assessed within a single operative workflow. Current evidence suggests that FKPos is feasible, safe and associated with satisfactory early clinical outcomes. However, clear superiority over other alignment strategies remains unproven, and long-term data are still required. The three-pillar concept provides a practical framework for patient-specific TKA by integrating bony anatomy, ligament balance and patellofemoral function. Its application should remain within defined safe zones and be interpreted as a functional positioning strategy rather than a universal target.

Level V.