Are there differences in phenotypes between Asian and Caucasian osteoarthritic knees?

Given the increasing adoption of several personalized alignment strategies in total knee arthroplasty, it is essential to understand the distribution of Coronal Plane Alignment of Knee (CPAK) phenotypes within specific populations. This is one of the largest retrospective, cross-sectional study conducted in 2026 osteoarthritic knees to establish the distribution of CPAK types in Indian patients. Standardized, preoperative standing long-leg radiographs from hip-to-ankle were analyzed. Each knee was classified into one of the nine CPAK types based on the arithmetic Hip-Knee-Ankle angle (aHKA: varus, neutral, or valgus) and Joint Line Obliquity (JLO: apex distal, neutral, or apex proximal). There was a prevalence of varus alignment, with 76 % of knees demonstrating a varus aHKA (mean 5.12^o). Types I, IV, II, and V were most frequently seen (56.1 %, 19.1 %, 11.3 %, and 6.6 %, respectively). CPAK I was more common among the Asian countries. CPAK II was more common among the non-Asian countries. Further studies with longitudinal outcomes will enhance understanding of optimal alignment targets for personalized arthroplasty and whether restoring pre-arthritic phenotype will lead to superior outcomes.