An injection device comprising a housing comprising a cartridge received in a cartridge holder and the cartridge contains a medicament sealed in a barrel defining a longitudinal axis and the ends of the barrel are closed by a moveable plunger and a pierceable septum. The injection device further comprises a drive assembly having a curved piston rod configured for advancement of the plunger in the cartridge along the longitudinal axis from a retracted position to an extended position for expelling the medicament from the injection device. An interchangeable adapter is positioned between the curved piston rod and the plunger for transferring the load from the piston rod to the plunger during advancement, and a pivot bearing is formed between the end of the piston rod and the adapter
