Tibial metaphyseal-diaphyseal angle

The tibial metaphyseal-diaphyseal angle is measured on an anteroposterior standing radiograph of the knee as follows: 1) draw a line along the longitudinal axis of the tibia (line 1); 2) draw a line through the lateral peaks of the proximal tibial metaphysis (line 2); 3) draw a line perpendicular to line 1 at the intersection of lines 1 and 2 (line 3); 3) measure the angle between lines 2 and 3 (the tibial metaphyseal-diaphyseal angle). A tibial metaphyseal-diaphyseal angle ≤11° suggests physiologic rather than pathologic bowing. In this patient with Blount disease, the tibial metaphyseal-diaphyseal angle is approximately 18°.