Traditional coronal alignment paradigms in primary total knee arthroplasty (TKA) have long championed systematic neutral mechanical alignment as the ultimate surgical target. The core tenet was simple: create perfectly balanced, rectangular flexion and extension gaps perpendicular to the mechanical axis of the lower limb to ensure uniform load distribution. While this classic technique has delivered exceptional long-term implant survivorship, notably hitting 82% out to 25 years, the patient-reported clinical reality has hit a stubborn, stagnant ceiling. Approximately 20% of modern knee replacement recipients remain actively dissatisfied, frequently complaining that their joint possesses an artificial, unnatural feel.
In an aggressive effort to break through this satisfaction plateau, the global orthopedic community has pivoted sharply toward personalized alignment strategies, such as constitutional, kinematic, and phenotypic alignment protocols. Central to this movement was the development of the Coronal Plane Alignment of the Knee (CPAK) classification system, an elegant matrix engineered to map individual lower-limb anatomy and native joint-line obliquity.
