A dynamic bone anchor for anchoring a spine stabilization assembly which supports the spine while providing for the preservation of spinal motion. The dynamic bone anchor provides load sharing while preserving range of motion and reducing stress exerted upon the bone anchors and spinal anatomy. The dynamic bone anchor includes a deflectable post connected by a ball joint to a threaded anchor. Deflection of the deflectable post is controlled by a compliant sleeve. The force/deflection properties of the dynamic bone anchor may be adapted to the anatomy and functional requirements of the patient. When implanted the pivot point for the deflectable post is placed close to the instantaneous center of rotation of the spine. The dynamic bone anchor may be used as a component of a dynamic stabilization system which supports the spine while providing for the preservation of spinal motion.