The invention relates to a piston rod drive arrangement for an injection device used for self-administration of a plurality of individually set doses. The drive arrangement is made from a first element (10) mating the non-circular cross-section (3) of a piston rod (1) and a second element (20) having an inner thread (21) mating the outer thread of the piston rod. Whenever the first element (10) and the second element (20) are rotated in relation to each other the piston rod (1) is moved in an axial direction. In order to minimise the play in the threaded connection a resilient element (23) is proved to apply a force to the piston rod (1) in a longitudinal direction.
