A mattress 10 comprising a base 20 with upper and lower surfaces 21, 22 and a frame 30 which surrounds at least a portion of a periphery of the base 20. The border 30 extends above the top surface 21 of the base to define a mattress cavity 40 for receiving an inflatable bladder 50. The mattress 10 may also include pluralities of channels 23, 25, 34 formed on the upper surface 21, lower surface 22 and frame 30 respectively. These grooves 23, 25, 34 allow the frame 30 and base 20 to bend and conform with an underlying support frame without placing the other parts of the mattress 10 under strain. The upper channels 23 may be divided into two sets of parallel recesses 23a, 23b extending perpendicular to one another, thus defining substantially square islands 24.
