COUPLED MOTION, ACCORDING TO LEHMKUHL AND SMITH:

"THE CONCAVE SIDE OF THE NORMAL CURVE TURNS TO THE CONVEX SIDE OF THE LATERAL CURVE.

A LATERAL BEND TO THE LEFT WOULD CAUSE ROTATION OF THE THORACIC VERTEBRAL BODIES TO THE RIGHT.

LUMBAR BODIES WOULD TEND TO ROTATE LEFT..."

THUS,

IN AN INTERVERTEBRAL SEGMENT THAT IS FLEXED:

• LATERAL FLEXION AND ROTATION OCCUR IN OPPOSITE DIRECTIONS:

• A LEFT LATERAL BEND IS ASSOCIATED WITH RIGHTWARD THORACIC ROTATION.

• (TYPE I COUPLED MOTION)

IN AN INTERVERTEBRAL SEGMENT THAT IS EXTENDED:

• LATERAL FLEXION AND ROTATION OCCUR IN THE SAME DIRECTION:

• A LEFT LATERAL BEND IS ASSOCIATED WITH LEFTWARD LUMBAR ROTATION.

• (TYPE II COUPLED MOTION)