"The posterior junction (or junctional) line is formed by the apposition of the pleural surfaces of the posteromedial surfaces of the upper lobes of the lungs, posteriorly to the oesophagus but anterior to the thoracic spine (usually T3-T5) 1,2. Unlike the anterior junction line, the posterior junctional line can extend well above the clavicles. It may contain intervening fat within 2."
"seen in ~30% of PA chest x-rays 1,2"
"There are many causes for an abnormal appearance of this line 1,2:"