Alignment and/or ligament balancing? Towards truly personalized total knee arthroplasty—A narrative review

Total knee arthroplasty has evolved from a purely mechanical procedure towards a more personalized restoration of each patient's native knee function. This narrative review explores the physiological and pathological patterns of knee laxity, the spectrum of alignment phenotypes and their interplay with ligament balancing strategies. It summarizes current evidence on physiological laxity envelopes, osteoarthritic alterations and alignment classifications such as Coronal Plane Alignment of the Knee, functional and laxity-based phenotypes. The review further examines how alignment philosophies affect soft-tissue tension and postoperative stability. Recent advances in robotic and sensor-assisted techniques have enabled objective intraoperative assessment of ligament balance, allowing reproducible quantification of medial-lateral gaps and compartmental pressures. These technologies reveal that individualized ligament behaviour often diverges from bony alignment, underscoring the need to define reproducible physiological balance targets. Functional outcomes appear optimized when medial stability and controlled lateral laxity are restored, supporting the concept of reproducing physiological asymmetry rather than enforcing symmetric gaps. However, existing studies remain heterogeneous and often underpowered, with conflicting results regarding the clinical impact of intraoperative balance on outcomes. Future research should rely on larger, prospective, high-level evidence studies to better define optimal alignment-balancing strategies and their translation into functional benefit. Level of Evidence: Level V.