Six-degree-of-freedom knee motion during treadmill walking in mechanically and kinematically aligned TKA.

The current literature remains inconclusive about whether kinematic alignment (KA) is superior to mechanical alignment (MA) in total knee arthroplasty (TKA). Therefore, this randomized controlled trial sought to provide further clarification. 39 MA patients, 33 KA patients, and 9 healthy controls were included. All participants underwent three-dimensional gait analysis on a treadmill one day before surgery and one year postoperatively. A preoperative range of motion (ROM) score was calculated and correlated with the postoperative Forgotten Joint Score (FJS). One year after surgery, no significant kinematic differences were observed between MA and KA. However, in Coronal Plane Alignment of the Knee (CPAK) type 1 patients, KA knees more closely reproduced the gait of healthy controls and showed higher walking speed. Correlation analysis revealed that patients with a higher preoperative ROM achieved better outcomes with KA, whereas female patients with lower ROM benefit more from MA. Although no kinematic differences were detected, the strong trend toward reduced joint space in MA compared to KA in CPAK type 1 patients may result from subtle deviations in joint-line restoration or postoperative soft-tissue tension. Both factors can affect load distribution and joint perception. The present findings support a patient-specific approach to alignment selection in TKA.