If you suspect infantile Blount’s disease and you measure the angle of Drennan what measurement should raise your suspicion?

The correct answer is C. The metaphyseal-diaphyseal angle (of Drennan) is an important measurement used to distinguish between tibia vara (Blount’s disease) and physiological bowleg.  An angle of more than 16 degrees predicts progression to infantile Blount’s disease while an angle of less than 11 degrees is an indicator of physiological genu varum. If you measure an angle between 11 and 16 you should reassess the patient after a few months.