The present invention relates to a protective sheath (1) for a cannula (4) arranged on a hub which can be fitted onto a syringe characterized in that:- said sheath (1) comprises a lock ring (2) located on the outer surface of said sheath (1)- said lock ring (2) is rotatable with respect to the sheath (1) between three positions:- a position before use (PBU)- a position during use (PU) and- a position after use (PAU).The present invention also relates to an injection system comprising a sheath according to the present invention and to a syringe comprising a sheath according to the present invention or an injection system according to the present invention.
