A segmented piston rod for an injection device includes multiple segments joined together via a hinge located on one side of each segment. The piston rod can be bent in one direction by articulating subsequent hinges while an axial force can be transmitted by the segmented piston rod to the stopper when the subsequent hinges are closed and the segments abut each other opposite to the one side of the hinge. The segmented piston rod is secured against rotation relative to the housing around the longitudinal axis of the segmented piston rod. The segmented piston rod has a last element which abuts the stopper in the reservoir and a first segment which is opposite to the last segment. The first segment is includes an internal thread matching an external thread of a drive sleeve and rotation of the drive sleeve advances the piston rod towards the stopper of the reservoir.
