Comments on: CPAK oversimplifies the complex 3D anatomy of the bony knee: Role of 3D CT for improved analysis – a schematic overview by S. Ram Sudhan et al.

We read with interest the recent article by Sudhan et al. on the limitations of the Coronal Plane Alignment of the Knee (CPAK) classification. While we agree with their emphasis on the shortcomings of two-dimensional radiographic analysis, we believe that CPAK limitations begin even earlier, at the level of its categorical structure. As a discrete, threshold-based system, CPAK projects continuous coronal anatomical variability onto a fixed 3 × 3 grid. Although practical and reproducible, this framework inevitably reduces anatomical granularity. Thus, CPAK limitations arise not only from omission of 3D information, but also from discretization of continuous coronal anatomy.