Differentiation is learning to move one segment, such as the pelvis, without the neighbors joining in.
A pelvis that cannot tip without the ribs thrusting, a head that cannot turn without the shoulder, a shoulder blade that cannot slide without the neck: the parts have forgotten they can act separately. In 📝Postural / Structural Realignment restoring that option is often the work — not stretching harder, but asking one piece to move while the rest stays. That is a motor and awareness finding, not a diagnosis of fusion or of a joint that is stuck as a medical fact.
Clients feel it as "everything comes with me." Practice is small, slow, and boring on purpose: a tiny pelvic clock, a quiet nod, a blade slide they can breathe through.
Pain, numbness, or a new loss of independent motion after trauma is a referral.