Principles of Manual Medicine
Normal Motion Mechanics
Normal vertebral motion can be characterized by the capacity of paired facets among groups of vertebrae to open and close. When we speak of the capacity of facets to open and close, we are referring primarily to a sliding-type movement that occurs during flexion (forward-bending) and extension (backward-bending), not a separation-type movement (Click here to visualize normal flexion and extension of L1-L5 from a side view, a back view, and a top view.
A pair of vertebrae define a motion segment. Motion of the superior vertebra is described relative to the inferior vertebra, and rotation of a vertebra is defined using the anterior surface of the vertebral body as opposed to the elements of the posterior arch. Click here to view normal flexion and extension of a vertebral motion segment.
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