A mattress retention assembly is disclosed that includes a mattress retainer system for retaining a mattress in place that is supported by an adjustable platform assembly and more particularly to a mattress retainer system that includes mattress retainer bars. The mattress retainer system is attached to the adjustable platform assembly. In order to secure the mattress relative to the adjustable platform assembly, one or more mattress retainer bars for the head and foot of the bed along with the corners of the bed are provided. In accordance with an important aspect of the invention, the mattress retainer bars are movable or removable to allow the mattress retainer bars to be positioned flush or below the top surface of the adjustable platform assembly to enable easy and convenient rotation, maneuverability, or otherwise sliding of the mattress relative to the platform. After the mattress is rotated, maneuvered, or slid, the mattress retainer is re-positioned to restrain movement of the mattress with respect to the adjustable platform assembly.