A group of ten former National Hockey League (NHL) players are suing the North American professional hockey league for not doing enough to prevent concussions and head injuries in their sport.

The lawsuit, which includes former All-Star defenseman Gary Leeman and former Toronto Maple Leafs Rick Vaive as plaintiffs, claims that NHL players were kept in the dark regarding the dangers of concussions since the league began their 1997 study into brain injuries through 2004. Leeman claims that since his retirement, he has suffered from post-traumatic head syndrome, headaches, memory loss and dizziness. Studies have linked multiple concussions and head injuries with chronic traumatic encephalopathy, a disease that includes symptoms such as memory loss and mood swings.

"The NHL's active and purposeful concealment of the severe risks of brain injuries exposed players to unnecessary dangers they could have avoided had the NHL provided them with truthful and accurate information and taken appropriate action to prevent needless harm," according to the lawsuit. 

The plaintiffs say that the NHL waited until 2010 to make targeting a player's head a penalty, continues to fail to ban body-checking and fighting while promoting a "culture of violence" through the use of "enforcers" whose only task on the team is to fight in the hockey rink.

"NHL rule changes in 2004 made the game faster, more exciting, and more marketable but led to increasingly violent collisions between players resulting in an unprecedented number of severe head injuries" said Steven D. Silverman, attorney for the former players. "The NHL still refuses to bar bareknuckle fighting or body-checking in spite of overwhelming evidence that both practices result in debilitating head injuries. Instead, the NHL prefers to continue employing and glorifying 'enforcers' - players whose primary role is to fight and violently body-check opposing players."

NHL commissioner Gary Bettman recently touted the league's commitment to taking head injuries serious since 1997, saying that the league has spent resources and worked with the players association to address player safety. Bill Daly, the league's Deputy Commissioner, said that the NHL intends to defend itself "vigorously" in a statement issued on Monday.

''We are aware of the class-action lawsuit filed today in the United States District Court for the District of Columbia on behalf of a group of former NHL players," said Daly in the league's official statement. "While the subject matter is very serious, we are completely satisfied with the responsible manner in which the league and the players' association have managed player safety over time, including with respect to head injuries and concussions."

Silverman said about 200 former players have signed up to be included in the class-action suit, with plaintiffs seeking monetary damages and NHL-sponsored medical monitoring for all league players who retired before February 14, 2013.

Some former players, such as former New Jersey Devil defenseman Ken Daneyko, former Detriot Red Wings & Philadelphia Flyers center Keith Primeau, and nine-time NHL All-star center Jeremy Roenick, have expressed no interest in joining the lawsuit, saying they knew what they got themselves into when they laced up their skates and hit the ice.

"I've always lived in the fact that I played the game of hockey knowing there was a lot of risk to be taken," said Roenick to the Associated Press on Tuesday, who says he suffered 13 concussions during his playing days. "I went on the ice knowing that my health and my life could be altered in a split second, and I did it because I loved the game."

The lawsuit against the NHL comes on the heels of the National Football League's (NFL) $765 million settlement with ex-players over a similar case against the football league. Michael McCann, a sports law professor at the University of New Hampshire, told USA Today that he believes the lawsuit against the NHL may not be as strong as the case against the NFL.

"Much of this complaint focused on how the NHL could've made the game safer at various points of time and how the league knew of information and didn't allegedly share it," said McCann. "In the NFL, there was the allegation that the league went out of its way to cloud the science. I didn't see any of that in this complaint. I saw the NHL could've done more and was interested in making money. Maybe there are ethical issues, but I don't see how that's necessarily a strong legal argument."