Functional Differences in the Affected Limbs Between CPAK Type I and Type II Patients Undergoing Unilateral Total Knee Arthroplasty

Background and Objectives: This study compared functional performance, gait performance, and dynamic balance between Coronal Plane Alignment of the Knee (CPAK) Type I and Type II patients undergoing unilateral total knee arthroplasty (TKA). Materials and Methods: We included 162 consecutive patients scheduled for unilateral TKA between January 2022 and August 2025. Patients were classified according to CPAK type; 42 were Type I and 33 were Type II. Preoperative assessments included demographic data, Korean Knee Score, and WOMAC. Functional performance was evaluated using the Timed Up and Go (TUG) test and the 4 m walk test. Isokinetic knee extensor and flexor strength (60°/s), hip abductor strength, and bilateral thigh circumferences measured 5 cm and 15 cm proximal to the patella were assessed. Dynamic balance asymmetry was evaluated using the POSTUROMED device. Inter-limb differences were calculated by comparing the operated and non-operated limbs. Results: No significant between-group differences were observed in clinical scores, knee extensor, or flexor strength deficits, hip abductor strength deficits, or thigh circumference differences. However, CPAK Type II patients demonstrated significantly better functional performance, with faster TUG (p = 0.014) and 4 m walk test times (p = 0.022). Dynamic balance outcomes were also significantly better in the Type II group (p = 0.042). Conclusions: Despite similar patient-reported clinical scores and muscle strength, patients with the CPAK Type II phenotype exhibited superior gait performance and dynamic balance compared with those with Type I following unilateral TKA.