The trunk movements proper take place in the joints of the lumbar and dorsal regions of the spine. Each of these joints has a very limited movement, but by combining their power of movement quite a large amount of mobility arises. On the whole, these movements, like the Neck and Head movements, take place round three axes, and we can thus divide them into Flexion and Extension round a frontal, Side-bending round a sagittal, and Rotation round a vertical axis.

On account of the structure of the small joints in the various parts of the spinal column, bending and stretching take place mostly in the lumbar region, side-bending mostly in the dorsal, and rotation chiefly in the joints between the tenth, eleventh and twelfth dorsal vertebrae.

Fig. 91.