When Browns safety T.J. Ward sent his shoulder crashing into Rob Gronkowski's outstretched right leg, everyone had the same two thoughts: "Holy shit, Gronk just tore his ACL!" and "Ward only went low because he didn't want to concuss Gronk and get fined for doing so." Well, try telling that second one to Gronk, who as it turns out was concussed on the play.
Here's where we step back and remember that there is no way to fix the violence of football. The league's continued attempt to eliminate brain damage from the game, which has mostly manifested itself in the form of draconian fines and suspensions, has certainly started to scare defenders away from going high. Torn up knee ligaments are the price we have to pay if we don't want free safeties concussing people with head shots, the thinking, however perverse, goes.
Except that's not at all how football works. The violence of the game can't be managed and channeled in ways that match the whims of the league, and Gronk's concussed brain is just the latest evidence of that fact. Concussions aren't a problem because of the prevalence of violent head shots, but because the game itself is really fucking violent and inherently harmful to the people who play it.