A foldable mattress support has an adjustable inner frame with a ratchet support for raising the head of a mattress. Legs are incorporated into the side and end bars of the mattress support. Upper and lower bars of the support are pivotally attached to the vertical plate of a hinge. Bolts oriented along axes of rotation pass through the bars and through the vertical plate. A first upper bar pivots about a first axis; a second upper bar pivots about a second axis; a first lower bar pivots about a third axis; and a second lower bar pivots about a fourth axis. Each of the axes is orthogonal to the vertical plate, and the third axis is spaced farther apart from the fourth axis than the first axis is spaced apart from the second axis. The distal ends of the upper and lower bars are pivotally attached to end bars.