Abstract: A rotationally pivotal motion controller pivotally interconnects two adjoining elements and controls the pivotal motion of a first of the two adjoining elements with respect to a second of the two adjoining elements. The rotationally pivotal motion controller comprises a housing having a wall which defines an axial cylindrical bore through the housing. The wall is adapted for attachment to a first of the two adjoining elements and the wall also has a longitudinal aperture therethrough which communicates with the bore. A hub assembly comprises a hub which is at least partially disposed within the cylindrical bore of the housing and is axially rotatable therein. The hub has a substantially central cylindrical core and at least one lobe extending radially from the core. At least one end cap is affixed to one end of the hub to retain the hub in a fixed, fluidically sealed, axial relationship within the housing. The hub and the housing together define at least one fluid retention cavity.