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Objectives and questions: The Coronal Plane Alignment of the Knee (CPAK) classification integrates mechanical limb axis and joint line obliquity, enabling patient-specific characterization of coronal alignment relevant for individualized total knee arthroplasty. This study aimed to stratify patients with end-stage knee osteoarthritis (KOA) according to CPAK types and to investigate associations between alignment phenotype and clinical as well as functional parameters within a dynamic, multidimensional assessment.

Material and methods: Sixty patients (55% female) with advanced KOA (Kellgren–Lawrence grade IV) scheduled for primary total knee arthroplasty were prospectively enrolled between 2024 and 2026. Baseline assessment included clinical examination (range of motion, stability), KOOS, and radiographic analysis (mLDFA, mMPTA, tibial slope). Joint Line Obliquity (JLO = mMPTA + mLDFA) and Hip–Knee Angle (HKA = mMPTA − mLDFA) were calculated, and alignment types were classified according to CPAK (Types I–IX; MacDessi et al., 2021). Static and dynamic analyses of stance, gait, limb alignment, pelvic and spinal posture were performed using a light-optical motion system (DIERS 4D motion lab). Group comparisons were conducted using Kruskal–Wallis tests with Dunn correction and Mann–Whitney U tests with Holm correction (α < 0.05).

Results: Mean age was 69 ± 9 years. Varus-dominant types accounted for 72.5% (Types I–III), neutral types 25.5% (Types IV–VI), and valgus types 2.0%. Radiographic findings were confirmed by optical analysis. Patients with distal joint line obliquity (JLO > 177°) showed significantly higher KOOS scores in ADL and symptoms. Knee flexion range of motion differed significantly between groups. Pedobarography demonstrated greater anterior load distribution in Type I vs. Type II (49.0 ± 6.7% vs. 43.6 ± 7.0%; p = 0.033) and larger plantar contact area in Type I vs. Type III (139.7 ± 22.2 vs. 109.8 ± 18.2 cm²; p = 0.015). Maximum plantar pressure differed between Types I and V. Dynamic pelvic and spinal analyses revealed significant alignment-dependent differences in pelvic obliquity (Type I: 4.7 ± 4.4 mm; Type II: 0.8 ± 2.5 mm; Type III: 0.4 ± 2.0 mm), pelvic tilt and torsion (Type I: −2.7° ± 2.3°; Type II: 1.2° ± 0.5°; Type III: −1.2° ± 3.5°), trunk posture (Type III: 8.1° ± 3.6°; Type V: 1.5° ± 5.2°; p = 0.048), and spinal rotation (Type III: −5.9° ± 7.1°; Type IV: 1.3° ± 4.1°; p = 0.047).

Discussion and conclusions: CPAK alignment types are associated with distinct functional and postural adaptations beyond static morphology. Coronal limb alignment phenotypes correspond to characteristic load distribution and pelvic–spinal movement patterns, supporting CPAK as a functional framework for alignment strategy selection and individualized rehabilitation in contemporary personalized total knee arthroplasty.