Which signs mean a player must come off after a head knock?

The Hockey Australia Concussion Policy (effective 1 January 2024) says to remove a player immediately, if safe to do so, after trauma.

Remove and do not return to play or training if any of these are present: loss of consciousness; a dazed, blank or vacant stare; no protective action in falling to the ground; behaviour change atypical of the player; seizure or convulsion, or lying rigid or motionless from muscle spasm; confusion or disorientation; motor incoordination; memory impairment.

Remove for further assessment if any of these are present: a possible occurrence of any sign above; a facial or head injury; lying motionless for over two seconds; balance problems or dizziness; headache; nausea; blurred vision; any other sign that the player is "not quite right".

A player does not have to lose consciousness to have a concussion, and symptoms can be delayed, appearing over the first 24 to 48 hours. Australian hockey recommends a conservative approach to removal.