A cannula for use in a terminable intraosseous device comprises a cannula body, and a penetrator-independent proximal bone penetration indicator (PBPI) associated with the body for positively indicating initial penetration into the proximal bone. In various embodiments, the PBPI comprises a roughened surface provided at a distal end of the cannula body to assist in increasing an amplitude of vibrations that are generated immediately upon contact with a proximal bone cortex during performance of an intraosseous injection, a resilient element fixed at one end which becomes plastically deformed, a visually indicative element which is exposed when the distance between the cannula body and penetrator is changed, or a frictionally engageable element. In some embodiments, a stopper prevents additional penetration into the proximal bone, and a reinforcing member inserted within a cannula body lumen reinforces a thin-walled portion of the cannula body.