Reproducibility and reliability of the anatomic axis of the lower extremity.

Two observers measured the tibiofemoral angle of 60 knees on hip-knee-ankle and anteroposterior (AP) knee radiographs and repeated the measurements 6 months later. Intraobserver reproducibility was moderate. Interobserver reliability was poor. These findings were the same irrespective of which radiograph was used during the measurement. Hence, although an AP knee radiograph was as reliable and reproducible as the hip-knee-ankle view, the radiographic tibiofemoral angle should not be considered a precise measurement.