The back of a wheelchair user is independently supported along and about three mutually perpendicular axes. Two elongated adjustment arms are pivotally connected to extension arms which telescope into opposite ends of a hollow connecting tube. The support positions along and about the three axes is achieved by pivoting the arms and the connected relationships of a back shell and cushion to the connecting tube, while the adjustment arms remain pivotally connected to the wheelchair and the extension arms are telescopically retained in the connecting tube.