We propose a surgical technique for structural allograft reconstitution of the diaphysis of long bones, maximizing surface contact between host and allograft bone. This method, analogous to a telescope, overlaps the graft and host bone, theoretically increasing bone surface contact substantially. We report the outcome of 22 telescoped allograft junction sites in 19 patients who lacked sufficient host bone to accommodate a regular-length stemmed implant. This joint-sparing reconstruction preserved 15 of 16 adjacent joints at risk for replacement. Five patients needed additional surgery, but none for nonunion. The diaphyseal length could be reconstructed enough so that a short prosthesis (less than the critical 40% of total bone length) could be used. This biologic method to reconstruct major segments of the diaphysis is best suited for patients with quantitatively or qualitatively deficient residual bone stock after tumor resection or prosthetic revision. We believe it is an excellent technique for revision knee megaprostheses when there is a short remnant of proximal femur.