Woven and knitted cardiovascular prostheses are tubular structures made of polyester filaments. They are used as bypasses to derive blood circulation or to replace failed blood vessels. The conditions of use require particular mechanical properties of the graft, such as elasticity and bending. A theoretical model, based on elasticity hypotheses, and a pulsatile flow system were used to determine the mechanical behavior of a knitted vascular graft under fluid pressure. For steady flow, prosthesis bending evolves in direct ratio to pressure. In pulsatile flow conditions, the prosthesis bends but not in proportion to the fluid pressure, showing instead a viscoelastic behavior by the textile structure.