Matthew Masifilo was a sophomore defensive lineman at Stanford in 2009 when he tore the MCL in his knee. The swelling and pain were horrible, he says. To lower his discomfort, and get him back on the football field, team doctors did what they often do in those situations. They prescribed Vicodin.

"I wouldn't take it," Masifilo said. "I always reacted badly to it. So I stuck with the old ways."

The "old ways" featured regular consumption of kava, a ceremonial drink at the center of Polynesian culture. Made from the root of a native plant, kava is viewed largely as a social lubricant that delivers a calming, mellowing effect. But Masifilo considers it a natural pain reliever and anti-inflammatory agent as well, a substance that is far less dangerous than opioids and doesn't carry the legal hurdles of marijuana.

What is kava? Kava is a root that grows on South Pacific islands. For thousands of years, Polynesians have pulverized it and mixed the powder with water in a ceremonial bowl. The drink provides a center of communal interaction and delivers a calming effect that makes it an anti-anxiety agent and perhaps a pain-reliever and anti-inflammatory as well.

After retiring from a five-year NFL career in 2015, Masifilo has employed his Stanford engineering degree to deliver kava to football players -- and anyone else -- who want natural options amid the national opioid crisis. He invented a shaker bottle, which he calls an AluBall, to simplify the preparation process and encourage individual use at a time when kava consumption is spiking around the country.

"With the opioid crisis, there is a big need for other options," said Masifilo, who was born in Hawaii but is of Tongan descent. "The doctors used to think I was crazy when I said I wanted to treat my injuries with kava. But it helped me, and I think it has the potential to help address this painkiller problem we have in football and many other sports."

Thomas Keiser, for one, can provide powerful testimony. Masifilo introduced him to kava at Stanford, and Keiser said he "truly embraced it for pain management" during his second year in the NFL. As a linebacker for the Carolina Panthers in 2012, Keiser suffered a series of injuries that sound like they were caused by a car accident rather than football.

First, he endured an impact injury on his leg that required a sizable piece of flesh to be removed. The area got infected, causing pitting edema and then swelling throughout the leg. As he played through it, with the help of painkillers, he then tore the UCL in his left elbow when a collision pushed his arm backward. Braced and taped, he continued playing in that game -- until he tore the UCL in his right elbow while trying to protect the left.

With a swollen leg and two torn UCLs, Keiser said he was "on lots and lots" of painkillers.

"One day I was like, 'This is probably not a good path to be going down,'" said Keiser, who retired after the 2015 season. "Kava was absolutely a better alternative for me. To this day, it's still part of my routine. I've taken painkillers and I've used kava. To me, opioids weren't as much about relieving pain as they were almost just getting you high to take your mind off of the pain. Whereas, to me, kava feels like the actual addressing of pain."

"To me, opioids weren't as much about relieving pain as they were almost just getting you high to take your mind off of the pain," former NFL linebacker Thomas Keiser said. "Whereas, to me, kava feels like the actual addressing of pain." Jeff Siner/Charlotte Observer/Getty Images

There is little clinical research on kava as a painkiller or anti-inflammatory, according to Dr. D. Craig Hopp, the deputy director of the division of extramural research at the National Center for Complementary and Integrative Health. Research does suggest, however, that kava works as an anti-anxiety agent -- what Hopp called "herbal Xanax."

Can diminished anxiety contribute to less pain? Perhaps.

"If you're more calm or relaxed," Hopp said, "if you aren't stressed about the pain you're under, that might help indirectly with the perception of its benefit. There isn't much direct evidence of it as a pain reliever, but that might be an indirect link."

There are no clinical indications of addictive properties, and Hopp said: "But I think kava is a much safer alternative in most circumstances than opioids."

And while opioids are addictive and can destroy organs, there is little clinical concern for the safety of kava. In 2002, the Federal Drug Administration issued a consumer advisory that warned of possible liver damage. But those concerns have subsided, Hopp said, amid uncertainty about whether kava caused liver damage during research or if another substance did.

In recent years, in fact, kava bars -- public establishments where kava is served instead of alcohol -- have popped up around the country. The company Kalm with Kava has tracked the opening of 82 such bars in the U.S. Keiser said that many of the people he meets at kava bars say they are recovering opioid addicts. Indeed, Kopp said, "The things I'm aware of suggest that kava usage is the highest that it's ever been."

That's a trend Masifilo will continue to try to bring to NFL locker rooms. Between the two of them, Masifilo and Keiser played for four different franchises. At one point or another, all of them had a group of players who would sit in the locker room after practice, drinking kava and talking. Kava helped alleviate the pain from the physical grind of the season, but the team-bonding benefits were just as significant, Keiser said.

Kava is a legal substance, according to U.S. law and NFL policy. Masifilo said some players have tried to keep their use "hush-hush," but by all accounts, it has been welcomed by team officials who have noticed it.

Among them is New England Patriots owner Bob Kraft, who in 2014 counted 18 players drinking kava in the locker room after a late-season practice. That team included two prominent players of Polynesian descent, tight end Michael Hoomanawanui and defensive lineman Sealver Siliga. Kraft credited the kava gatherings with helping to build unity on a team that went on to win Super Bowl XLIX.

"It was late afternoon," Kraft said, "and they were just joshing around and having fun. It was really special."

Made from the root of a native plant, kava is viewed largely as a social lubricant that delivers a calming, mellowing effect. But some think it can help offer relief as a painkiller as well. Courtesy of Matthew Masifilo

It is no secret that NFL players are desperate for pain relief, both during their career and afterward. Keiser, who played in a total of 40 NFL games, deals with the aftereffects of not only the elbow injuries, but also ankle and knee ligament tears, along with herniated discs in the lumbar, thoracic and cervical parts of his spine.

"I have major pain issues from the various injuries of my career," he said, "I absolutely drink kava now and love it for the pain. It's also a social drink, and it's nice to get together with your boys and drink it for the social aspect of it.

"The big thing is that painkillers are far too common in football. This is a far better alternative to all the opioids. I can definitely speak from experience on that."