A radially expandable stent-graft endoprosthesis includes a knitted tubular structure circumferentially disposed and securably attached to the stent. The knitted tubular structure has a warp knit pattern of interlacing yarns with at least a two-needle underlap to provide greater than 50 percent longitudinal stretchability while substantially inhibiting dilation. A knitted tubular graft is combined with an ePTFE liner to form a composite with greater than 50 percent longitudinal stretchability is also provided. The knitted tubular graft also has a warp knit pattern of interlacing yarns with at least a two-needle underlap to provide the longitudinal stretchability while also substantially inhibiting dilation.