Police say a video circulating on social media which appears to show an officer kicking a man in the head only shows part of his arrest.
Superintendant Lane Todd, Canterbury Metro Area Commander, said the "interaction" occurred in Christchurch on March 2.
He said police were called on two separate occasions, in a short space of time, to a Madras St address following reports of an aggressive and intoxicated man.
After being placed in handcuffs, Todd said the man began to actively resist the two officers and was taken to the ground in an attempt to keep everyone involved safe.
Todd said as the officers attempted to get the man to his feet, he allegedly kicked one of the officer's in the head.
"The second officer attempted to control the man but was also allegedly kicked in the head by him," he said.
"Following this, one officer attempted to place the sole of his foot on the man’s shoulder however the man has moved, causing the officer’s foot to connect with his head once."
Todd said the video circulating on social media was a "small excerpt" from a fast moving and dynamic situation.
He said police had the full video of the incident, including audio, and had investigated the circumstances of it.
"It is important to note that short videos of police incidents often exclude relevant context."
Todd said both officers were later seen by a doctor for minor head injuries.
A 44-year-old man appeared in the Christchurch District Court facing two charges of assaults police and one charge each of resists police and disorderly behaviour.
He was due to reappear on May 31 for sentencing.