A syringe assembly comprising: a syringe barrel having an inside surface defining a chamber, an open end, and a distal end; a plunger rod assembly including a proximal flange, an elongate body portion, at least one recess along said elongate body portion, a stopper connected to said elongate body portion, said elongate body portion extending from said stopper to said proximal flange and a plurality of first teeth formed within said at least one recess on said elongate body portion, said first teeth defining a plurality of distally facing shoulders; and a locking element slidably positioned within said chamber along said elongate body portion, said locking element engaging said inner surface of said syringe barrel such that said locking element is substantially immovable in the direction of the open end of said syringe barrel and engageable with said plunger rod assembly such that said plunger rod assembly and locking element are movable distally together toward the distal end of the syringe barrel; wherein said plurality of distally facing shoulders being equally spaced along a majority of said elongate body portion; said locking element is disposed within only one of said at least one recess of said elongate body portion of said plunger rod assembly; and said elongate body portion further comprising: a second tooth having a smaller longitudinal length than the first teeth and defining an intermediate distally facing shoulder provided between a first and second distally facing shoulder, said first and second distally facing shoulders being positioned most distally on said elongate body portion among said plurality of distally facing shoulders; or at least one raised step and/or at least one indentation on an angled surface of a distal-most first tooth, wherein the angled surface extends proximally from a top of the distally facing shoulder of a distal-most first tooth to a base of an adjacent distally facing shoulder and said at least one raised stop and/or said at least one indentation having a smaller longitudinal length than the first teeth. a syringe barrel having an inside surface defining a chamber, an open end, and a distal end; a plunger rod assembly including a proximal flange, an elongate body portion, at least one recess along said elongate body portion, a stopper connected to said elongate body portion, said elongate body portion extending from said stopper to said proximal flange and a plurality of first teeth formed within said at least one recess on said elongate body portion, said first teeth defining a plurality of distally facing shoulders; and a locking element slidably positioned within said chamber along said elongate body portion, said locking element engaging said inner surface of said syringe barrel such that said locking element is substantially immovable in the direction of the open end of said syringe barrel and engageable with said plunger rod assembly such that said plunger rod assembly and locking element are movable distally together toward the distal end of the syringe barrel; wherein said plurality of distally facing shoulders being equally spaced along a majority of said elongate body portion; said locking element is disposed within only one of said at least one recess of said elongate body portion of said plunger rod assembly; and said elongate body portion further comprising: a second tooth having a smaller longitudinal length than the first teeth and defining an intermediate distally facing shoulder provided between a first and second distally facing shoulder, said first and second distally facing shoulders being positioned most distally on said elongate body portion among said plurality of distally facing shoulders; or at least one raised step and/or at least one indentation on an angled surface of a distal-most first tooth, wherein the angled surface extends proximally from a top of the distally facing shoulder of a distal-most first tooth to a base of an adjacent distally facing shoulder and said at least one raised stop and/or said at least one indentation having a smaller longitudinal length than the first teeth. a second tooth having a smaller longitudinal length than the first teeth and defining an intermediate distally facing shoulder provided between a first and second distally facing shoulder, said first and second distally facing shoulders being positioned most distally on said elongate body portion among said plurality of distally facing shoulders; or at least one raised step and/or at least one indentation on an angled surface of a distal-most first tooth, wherein the angled surface extends proximally from a top of the distally facing shoulder of a distal-most first tooth to a base of an adjacent distally facing shoulder and said at least one raised stop and/or said at least one indentation having a smaller longitudinal length than the first teeth.