Luke Kuechly walks off the field after suffering a concussion earlier this season. (USATSI)

The NFL's concussion problem isn't going away. By the numbers, it's getting worse.

That's according to the NFL, which released a report on Friday that revealed concussion data from the past four seasons. After seeing a decrease in concussions from 2013 to 2014, this past season experienced a sharp rise in the number of diagnosed concussions. Including practices, preseason games, and regular-season games, the increase was nearly 32 percent. In regular-season games only, concussions rose by 58 percent. In total, the NFL counted 271 concussions in 2015.

According to the Associated Press, NFL senior vice president of health and safety policy Jeff Miller said that one explanation for the sharp increase might be "unprecedented levels of players reporting signs and signals of concussions," meaning the increase could be due to heightened awareness and more frequent testing. Miller noted that the number of players tested for concussions doubled and that the league will continue to look into the potential causes.

A screenshot of a portion of the NFL's report (done by Quintiles Injury Surveillance and Analytics) is below, and you can read the entire report here.

The NFL saw a sharp rise in concussions in 2015. (NFL communications)

Some other notable numbers:

  • 92 of the 182 concussions (regular-season games only) were caused by another helmet.

  • In the past four years, helmets have always been the leading cause of concussions in regular-season games.

  • This season also saw an increase in ACL sprains (49 in 2014 compared to 56 in 2015) and MCL sprains (139 in 2014 compared to 170 in 2015).

  • In the past four seasons, the injury rate per game has been higher for Sunday and Monday games, while Thursday games have experienced a lower rate.

Before the season, a new NFL rule granted concussion spotters the power to stop a game if they saw a concussed player. But the league's concussion protocol still came under scrutiny, namely when Rams quarterback Case Keenum clearly suffered a brutal head injury but didn't immediately come out of the game. And, earlier in the year, Eagles defensive back Malcolm Jenkins admitted to playing through a concussion.