PBS Frontline investigation of the NFL's concussion crisis, "League of Denial" (2 hr)PBS Frontline, Season 32: Episode 2 The National Football League, a multibillion-dollar commercial juggernaut, presides over America’s indisputable national pastime. But the NFL is under assault: thousands of former players have claimed the league tried to cover up how football inflicted long-term brain injuries on many players. What did the NFL know, and when did it know it? In a special two-hour investigation, FRONTLINE reveals the hidden story of the NFL and brain injuries.