In the NFL, injuries are inevitable. But it’s not always the monster tackles that leave players hobbled and your fantasy team in limbo.

Sometimes, the biggest injuries come from the fields themselves. Specifically, turf fields.

The NFL Players Association has been fighting to get the league to move to all grass fields for years now, but the wealthiest league in the world — which made $12 billion last year alone — is too cheap to ban the most dangerous kinds of turf.

Instead, they celebrate it.

What’s happening?

Half the NFL uses grass fields, while the other half plays home games on turf. A study earlier this year found that playing on artificial turf produced a 28% higher rate of non-contact lower body injuries.

Sports Orthopedic Surgeon at NYU Langone Dr. Spencer Stein told More Perfect Union that foot and ankle injuries pose a particular threat on artificial surfaces.

“It’s kind of like running on concrete,” Stein said. “If you’re running on concrete a lot, it’s a lot of wear and tear. You can hurt your joints, your ankle. Whereas if you’re running on a softer surface — or like a grass surface — there’s more give, there’s more cushion.”

Former NFL offensive lineman JC Tretter currently serves as the president of the NFL Players Association. He believes owners are motivated to keep turf because of other money-making opportunities.

“So they would prefer to be able to host concerts and monster truck rallies and different events. And it’s easier to do that when your field is plastic and you can put things over top of it,” Tretter said. “They want to be able to use these stadiums for other reasons.”

Many stadiums with real grass do host events like concerts and monster truck rallies. The Raiders’ Allegiant Stadium, for example, employs the use of a field that can be rolled in and out as needed.

The other “football”

Owners aren’t unwilling to use real grass when it comes to soccer. FIFA and the World Cup require games be played on grass.

“And that’s where we get in this crazy world that players just cannot wrap their heads around,” Tretter told More Perfect Union. “Where these owners are willing to rip up the turf, put in grass, and then once the soccer players are done, rip up the grass and put back down turf for the NFL players to play on.”

In many cases, public tax dollars will be subsidizing these temporary conversions.

In Texas, the state is giving away millions in tax breaks to teams so they can upgrade their stadiums for the World Cup. That means the public is paying for ultra-wealthy Cowboys owner Jerry Jones to install special lights to grow grass for the soccer tournament, only to rip it up and put turf back down again for the NFL season.

What now?

The NFLPA is asking fans to stand up and petition owners to protect players.

Tretter said fans’ voices matter in this fight.

“As fans, they wanna see the best players in the world play,” he said. “And if there’s a surface out there that’s decreasing the likelihood for the paying customer to see the best players in the world play, then they should speak up to ensure that when they buy a ticket, they have the highest likelihood of going to that game and seeing these stars and these amazing athletes that can do things that nobody else on this planet can do.”