Finally at the twelfth rib! The twelfth rib is a floating rib (as is the eleventh) due to having no attachment to the sternum. As with the eleventh rib, the twelfth acts very much as a fulcrum for the ribs above when its inferior musculature contracts to fix it in place.
The muscles attached to the twelfth rib are: serratus posterior inferior, iliocostalis thoracis, iliocostalis lumborum, levator costae, diaphragm, internal intercostal, external intercostal, latissimus dorsi, external oblique, and (most notably) quadratus lumborum.
The nerves related to the twelfth rib are: the anterior and posterior divisions of the twelfth thoracic nerve, the sympathetic chain ganglia, the twelfth thoracic sympathetic ganglion, the recurrent meningeal nerve, and the least splanchic nerve.
The circulatory structures associated with the twelfth rib are: the intercostal artery and vein, the mediastinal artery and vein, the azygos and hemiazygos vein, the bronchomediastinal lymphatic duct, and the thoracic lymphatic duct. Continuing with the idea presented about ribs superior to the twelfth, I will suggest that the connection of the twelfth rib with the diaphragm also has the ability to effect the descending aorta, the inferior vena cava, the phrenic arteries and veins, as well as the superior mesenteric artery.
Just as an outline, the viscera and other structures associated with the twelfth rib (via sympathetic nerves) are: the middle gastrointestinal tract, the lower gastrointestinal tract (think large intestine), the kidneys, the upper ureters, the bladder, the uterus, the cervix, the erectile tissue in males and females, and the legs (as low as the greater trochanter).
The way I have written this may not be the most illustrative but I hope it is clear that rational treatment of the ribs requires the principle of treating from the base up and the center out. Without that principle the rib lesion will continue to influence related conditions by virtue of an imbalanced pelvic complex. That is why, at the CAO, the full body is always treated according to that principle. When asked what method is applied to a specific condition anywhere in the body, my response, as well as Mr. Robert Johnston’s, is: Osteopathy (as set forth in the principles outlined by A.T. Still).