The Coronal Plane Alignment of the Knee Classification: How It Works, How to Apply It, and How It can Affect Outcomes in Knee Reconstruction Surgery.

» 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.