A mattress or mattress topper includes a cushioning element having an elastomeric material forming intersecting buckling walls that define hollow columns, and a knitted fabric disposed over the cushioning element and configured to move independently of the buckling walls. The elastomeric material includes an elastomeric polymer and a plasticizer. The knitted fabric includes a first layer of stretchable material; a second layer of stretchable material; and a layer of stretchable fill material between the first layer of stretchable material and the second layer of stretchable material. The first layer of stretchable material is knitted together with the second layer of stretchable material as a unitary sheet of fabric including the layer of stretchable fill material. A method of forming a mattress or mattress topper includes disposing a knitted fabric over a cushioning element comprising intersecting buckling walls and configuring the knitted fabric to move independently of the buckling walls.