Background: In recent years, there has been considerable interest in prosthetic alignment techniques for total knee arthroplasty (TKA), particularly in the so-called kinematic alignment, which aims to restore the knee’s native alignment. However, implementing this technique requires specialized instruments and procedural steps that can be laborious. This study introduces the bisector of the trochlear groove as a reliable landmark for performing the distal femoral cut while maintaining parallelism with the native femoral joint line. Methods: Three orthopedic specialists assessed 110 X-ray images of full-leg, weight-bearing lower limbs obtained from healthy individuals between January 2021 and December 2022. The bisector of the trochlear groove was identified on the X-ray images, and the angle between this bisector and the femoral joint line was measured. The consistency of these measurements across repeated assessments and different examiners was evaluated. Results: The bisector of the trochlear groove was found to be perpendicular to the femoral joint line, with a mean angle of 89.4°. The inter-rater reliability was 68% within ±1.3° from the mean, while the intra-rater reliability was 82% within ±1.5° from the mean. Conclusions: These results suggest that by performing a femoral cut perpendicular to the bisector of the trochlear groove, surgeons can inherently restore the femoral joint line of the native knee in patients where the native joint line is no longer identifiable due to the effect of osteoarthritis. This method may offer a viable and straightforward alternative to the standard surgical technique currently practiced for kinematic alignment in TKA.

Background: There is a growing interest in TKA components alignment, especially around the kinematic technique, which aims at reestablishing the alignment of the native knee. However, the practical application of this technique has some limitations; (2) Methods: A series of consecutive full weight-bearing lower limbs radiographs performed in our Hospital without signs of osteoarthritis, post-traumatic deformities, and any previous surgical procedure (e.g. any joint replacement , osteotomy, anterior cruciate ligament reconstruction) were included. Several radiological parameters as the bisector line were measured by three members of our orthopedic unit and were then used to assess the inter-observer reliability.; (3) Results: 110 radiographic images belonging to 59 patients (both legs for 51 patients and one leg for 8 patients) were finally included in the present analysis. The bisector of the trochelar groove was perpendicular to the femoral joint line (mean 89.4°).; (4) Conclusions: The main finding of the current study was that the new anatomic landmark investigated, the bisector of the trochlear groove, was perpendicular to the femoral joint line viewed in the AP weight-bearing radiograph of the entire lower limbs of the healthy knee and therefore could potentially simplify the achievement of the kinematic alignment during a TKA procedure.