Describe how maintaining the head in normal vertical alignment (head/optical righting) causes the pelvis, spine, and joints of the lower extremities to behave as part of a closed kinematic chain

What will be an ideal response?

ANS: Because, in most instances, the head is maintained in an upright position with a vertical
orientation, the head is in essence fixed along a vertical axis. When one of the body segments in
weight-bearing throws the head out of alignment, the adjacent body parts will do whatever is
necessary to get the head aligned over the sacrum as closely as possible, because this minimizes
bony stresses. If the head is aligned properly over the sacrum in both the sagittal and the frontal
places, the spine is considered to be neutral or compensated. For example, if the hips are being
pulled into flexion by tightness in the iliopsoas (anterior pelvic tilt), the trunk does not remain
forwardly flexed on the anteriorly tilted pelvis. Instead, compensation occurs by extending the
lumbar spine. Similarly, if there is a short leg on the right, bilateral stance would tip the trunk and
head to the right. Instead, the spine compensates by laterally flexing to the left, and if necessary,
the cervical spine fine-tunes the positioning of the head vertically by laterally flexing to the right
again.