John Hunter's operation for popliteal aneurysm.

An aneurysm is defined as a "sac communicating with the lumen of an artery" and the treatment of the various types of this disease has intrigued surgeons through the ages. Aneurysms of the popliteal artery today are fairly uncommon. However, in the 18th century they were quite frequently encountered, many of them in coach drivers. We can only surmise that this was the result of repetitive trauma to the artery, already the seat of arteriosclerosis, against the rim at the top of the long leather riding boot which was worn at that time.