Figure 2. . (a) The anatomical transepicondylar axis (TEA) was defined as the blue line. The sagittal plane perpendicular to the TEA was defined as the true-sagittal plane (tsP) (yellow line). (b) The sagittal longitudinal axis (purple line) and the tangent line to the femoral posterior cortex drawn parallel to the sagittal longitudinal axis (greenline). (c) Measurement of lateral posterior condylar offset.