Image copyright AP Image caption Dan Marino played for the Miami Dolphins for 17 seasons

Legendary American football quarterback Dan Marino has sued the National Football League, alleging it hid the danger of head trauma from its players.

Mr Marino, 52, and 14 other ex-players filed legal action in Philadelphia last week, seeking damages for "negligence [and] intentional misconduct".

More than 4,500 former players had previously sued the league, reaching a $765m (£490m) settlement last August.

That settlement was rejected by a federal judge in January.

The plaintiffs in the new suit allege long-term and chronic injuries as well as financial losses resulting from head injuries suffered while playing in the National Football League (NFL), which is known for its violent play.

"Despite the NFL's knowledge of such dangerous practices and the increased risk of head injury to the players, the NFL turned a blind eye for decades, and allowed the players to be coached, trained and/or motivated to use any and all portions of their helmets to block, tackle, butt, spear, ram and/or injure opposing players with their helmeted heads," the players wrote in the suit.

Big hits

They say the NFL should have known of a connection between playing football and long-term health problems such as headaches, depression and dementia.

Marino played 17 seasons for the Miami Dolphins, retiring in 1999 to work as a sport broadcaster for CBS.

The NFL had previously agreed to fund concussion-related compensation, medical exams and research following a class action suit accusing the league of hiding research that had shown the harmful effects of concussions while glorifying and promoting violent play.

Helmet-to-helmet impacts are common in American football as strong, heavy and fast-moving players collide on the field of play.

Studies have linked repeated concussions with chronic traumatic encephalopathy, a disease with symptoms including memory loss and mood swings.

The plaintiffs in that case included at least 10 members of the Pro Football Hall of Fame, the family of linebacker Junior Seau, who took his own life last year, and former Atlanta Falcons safety Ray Easterling, who filed the first lawsuit in 2011 but later killed himself.