An externally guidable intervertebral disc apparatus manipulates disc tissue present at a selected location of an intervertebral disc, comprising a catheter having a distal end, a proximal end, and a longitudinal axis, the catheter having an intradiscal section at the distal end of the catheter, the intradiscal section being extendible into the disc, having sufficient rigidity to be advanceable through the nucleus pulposus of the disc under a force applied longitudinally to the proximal end, having sufficient flexibility in a direction of the disc plane to be compliant with the inner wall, having insufficient penetration ability to be advanceable through the inner wall of the annulus fibrosus under the applied force; and a functional element located in the intradiscal section for adding or removing energy or a material at the selected location of the disc. Methods of using the apparatus are also disclosed.