2,377 Contributions. Flank Pain is a kind of pain which is mainly characterised by mild to severe aching in the part of the body situated between the back and upper abdomen.This condition is comm … only associated with problems in the kidney.here on a horses body is the flank?   Flank: Where the hind legs and the barrel of the horse meet, specifically the area right behind the rib cage and in front of the stifle joint.