Distribution of Phenotypes of Coronal Plane Alignment of the Knees and Functional Phenotypes in the Healthy Young Iranian Population: A Cross-Sectional Study Publisher



Razzaghof M^{1, 2} ; Soleimani M^{1, 2} ; Poursalehian M^{1, 2} ; Ayati Firoozabadi M^{1, 2} ; Mortazavi SA^{1, 2} ; Mortazavi SMJ^{1, 2} Show Affiliations
Source: Journal of Experimental Orthopaedics Published:2025

Abstract

Purpose: The functional phenotypes and the coronal plane alignment knee (CPAK) classification have recently been introduced. This study aimed to describe the phenotypes of normal knees in the healthy young Iranian population based on these systems. Methods: This cross-sectional study included 402 knees in 201 healthy young adults. Phenotypes were reported using hip–knee–ankle (HKA) angle, femoral mechanical angle (FMA) and tibial mechanical angle (TMA) for functional phenotypes and joint line obliquity (JLO) and arithmetic HKA (aHKA) for CPAK classification. Also, a distinct combination of knee alignment parameters (HKA, FMA and TMA) that reflects the functional alignment characteristics of the knee, as described by Hirschmann, was used. Statistical analysis was performed using the Student's t test. Results: The mean HKA, FMA and TMA were 176.03 ± 3.01°, 92.01 ± 2.77° and 86.52 ± 2.73°, respectively. All angles of female participants were significantly more varied compared to men (p < 0.05). The most common phenotypes were VAR(Varus)HKA3°, NEU(Neutral)TMA0° and NEUFMA0°. The distribution of the 10 most common functional phenotypes was not significantly different between men and women (p = 0.201). The most common CPAK types were type I (33.6%), II (26.6%) and III (16.7%), and types VII, VIII and IX were rarely seen (2.0% overall). The distribution of CPAK phenotypes significantly differed between men and women (p = 0.015), and CPAK type III was more frequently seen in women. Clinically, the predominance of varus phenotypes and the sex-specific differences observed underscore the importance of tailoring surgical alignment strategies to individual anatomy. Conclusion: In conclusion, our study reveals that knee alignment in the healthy Iranian population tends to exhibit neutral or mild varus characteristics, with significant differences between men and women. These findings suggest that ethnicity may play a role in the natural alignment of the knee, which has important implications for surgical planning and outcomes. Level of Evidence: Level III. © 2025 The Author(s). Journal of Experimental Orthopaedics published by John Wiley & Sons Ltd on behalf of European Society of Sports Traumatology, Knee Surgery and Arthroscopy.