MacDessi, Samuel J.

Abstract » The coronal plane alignment of the knee (CPAK) classification is a practical and straightforward framework to define a patient’s constitutional coronal knee limb alignment and joint line obliquity. » Patients are assigned to one of nine phenotypes using two straightforward calculations; the arithmetic hip-knee-ankle angle (aHKA) and the arithmetic joint line obliquity (aJLO). » CPAK allows clear understanding of the geographical and gender variations in knee alignment, as well as the differing outcomes of knee reconstructive surgery, based on phenotype. » CPAK enables surgeons to tailor their alignment strategy to best fit a patient’s constitutional phenotype and avoid the drawbacks of a “one-size fits all” approach.

Orthopaedic surgeons are currently faced with an overwhelming number of choices surrounding total knee arthroplasty (TKA), not only with the latest technologies and prostheses, but also fundamental decisions on alignment philosophies. From ‘mechanical’ to ‘adjusted mechanical’ to ‘restricted kinematic’ to ‘unrestricted kinematic’ — and how constitutional alignment relates to these — there is potential for ambiguity when thinking about and discussing such concepts. This annotation summarizes the various alignment strategies currently employed in TKA. It provides a clear framework and consistent language that will assist surgeons to compare confidently and contrast the concepts, while also discussing the latest opinions about alignment in TKA. Finally, it provides suggestions for applying consistent nomenclature to future research, especially as we explore the implications of 3D alignment patterns on patient outcomes. Cite this article: Bone Joint J 2023;105-B(2):102–108.