Emergency Room personnel rated the majority of the injuries as minor or moderate. Less than 4% of the injuries were caused by gunshots, while slightly more than 3% involved cutting or stabbing wounds.
"As a physician and an injury researcher, I see these injuries as a health and public health problem, and I know that we cannot begin to improve until we understand the real extent of any medical problem," said Dr. Elinore J. Kaufman, lead author of the study and a physician at New York-Presbyterian Hospital Weill Cornell Medicine. "There has been a lot of attention to deaths involving police, but nonfatal injuries are little understood and much more common."
Kaufman and her colleagues used the Nationwide Emergency Department Sample to examine the period from 2006 through 2012 and found a total of 355,600 ER visits related to police injuries during the period.
The majority of injured patients, about 86%, were men. The average age of ER patients was 32.
"This is still a young population," said Kaufman in an email. She noted that 32 may be "slightly older than expected, indicating that this phenomenon is not limited to youth."
Two-thirds of recorded injuries from police officers occurred in the South and West, while the Northeast contributed about 17% to the total and the Midwest about 16%. Most injuries resulted from being struck, which could include being struck by an officer's baton, hand or even car..
"We cannot say for sure that there are no repeat visits," said Kaufman, adding that it is unlikely that a repeat visit by the same person would be included given how she and her colleagues made their calculations.
Slightly more than 63% of the police-injured patients lived in zip codes with median household income below the national average, while a clear majority, 81%, lived in urban areas. Nearly 61% were uninsured.
About 97% of the ER visits scored less than 9 on the injury severity scale, "the gold standard for judging injury severity," said Kaufman. This score "would be minor-moderate injury," said Kaufman.
Among the patients injured by police, nearly 16% were diagnosed as intoxicated, dependent or abusing alcohol or drugs.
One in five of the injured were diagnosed as having a mental illness while in the ER.
According to Darrel W. Stephens, executive director of the Major Cities Chiefs Association, a professional organization for police executives in the U.S. and Canada, the total number of injuries per year "does not seem unreasonable --about 140 a day between 18,000 police departments with mostly minor injuries."
"The problem is national data for an issue like this is not all that helpful," Stephens wrote in an email. "It is doubtful that these incidents are evenly distributed between departments or even within communities."
He added that police departments also keep statistics on injuries to individuals in custody or in the process of being arrested.
"Not all injuries in which treatment is sought is caused by police officers," said Stephens. "It in not unusual for police to transport individuals who have been injured to the emergency room."
Ted Miller, senior research scientist at the Pacific Institute for Research and Evaluation, noted the figures for alcohol, drug or psychological problems are an "undercount" since ER doctors only record a diagnosis of mental illness or substance use when they see a problem.
"They look at your condition and they may notice that you're bipolar and you're off your medication," said Miller, who was not involved in the study. "They may notice that you're drunk or that you're high on PCP and they've got to treat that PCP because you're not under control, so they record that diagnosis."
Emergency room staff do not check everybody for mental illness or substance use, said Miller.
Looking at the percentage of those diagnosed as mentally ill, Miller noted that "20% is a large number, especially when you know that it's an undercount."
In his own research on injuries caused by police
, Miller came to similar conclusions as the authors of the current study.
"I'm not at all surprised that they found that [the numbers are] basically constant over time, because that's what we found too," said Miller. He also suspected, from his own work, that there might be regional differences.
Based on his own research and knowledge of past studies, Miller noted that "police were not particularly administering undue force."
"When the police arrest you, if you resist, the proper procedure is basically to force you to the ground with your hands behind you and get handcuffs on you," said Miller.
Sometimes people fall down or get pushed down, observed Miller.
"And that gets you scrapes and bruises and sometimes a broken bone," said Miller. "And sometimes that gets the police scrapes and bruises and broken bones."
"Stops that go wrong are how people get injured," Miller said.
This appears to be true for cops as well as citizens based on the FBI's calculation of injuries
suffered by officers who have been assaulted.
Looking at when officers are injured -- not citizens -- during an assault, the FBI found 14,565, or slightly more than 29%, of all assaulted police officers suffered injuries.
This is based on a total of 49,851 officers assaulted while performing their duties during 2013 -- a rate of 9.3 per 100 sworn officers for the year.
Nearly 15% of the officers who were assaulted with knives or other cutting instruments suffered injuries. Slightly more than 10% of those attacked with firearms were injured, while 27% of those attacked with other dangerous weapons were injured.
Almost a third of the officers who were hit by hands, fists, or feet also suffered injuries.
According to the FBI, most assaults on police officers occurred between 12:01 a.m. and 2 a.m -- the hours when many bars close.