The invention relates to a screw anchor for the concrete attachment in a railway sleeper and to the force-fit connection by means of a rail screw, comprising a threaded section (14) with external threads (18) disposed on the exterior of the screw anchor (10) and internal threads (19) disposed in the screw anchor; and an upper partial section (16) without external threads which is disposed in the mounted state close to the anchor opening (26). Said invention is characterized in that material with high elasticity is arranged in the upper partial section (16), said material, when in the mounted state, forms an elevation which extends in the upward direction over the upper side of the end surface (36) of the upper partial section (16) and reduces the free opening section of the inner chamber of the upper partial section (16).