A steerable ultra-low patient bed that incorporates a means for maintaining verticality of the caster stem at all height positions of the bed and a means for selectively locking the caster assemblies of the bed in a desired locking position. The means for selectively locking the caster assemblies may be actuated from either end of the bed using a central actuation mechanism. The bed according to the present invention has legs that are pivotally and translatably attached at their upper end to a frame of the bed and caster support members that are longitudinally aligned with the bed pivotally attached to the lower end of each leg. The caster support members each have a single caster assembly attached thereto. The means for maintaining verticality of the caster stem incorporates a constraint means that urges the caster support member in a direction of rotation opposite to that of the leg during adjustment of the height of the bed.