||Haematomas of the auricle are usually the result of blunt trauma such as boxing, rugger and those other physical activities in which the skin of the pinna is exposed to twisting or shearing forces.
The skin of the lateral surface of the auricle is tightly attached to the underlying perichondrium, and the small blood vessels that lie between the perichondrium and the underlying auricular cartilage are easily ruptured by a shearing force.
Once a vessel is torn, blood will leak into the subperichondrial plane
(between the perichondrium and the cartilage), thereby elevating the perichondrium from the underlying cartilage.
This subperichondrial haematoma forms a soft blue or purple bulge that balloons the skin over the lateral surface of the pinna and distorts its normal sharp contours.