Before 12 preseason games kicked off on Thursday, NBA Hall of Famer Bill Russell re-emphasized his support of NFL players protesting social injustice during the national anthem.

Russell tweeted a picture of himself taking a knee with his Presidential Medal of Freedom hanging around his neck.

“The first NFL games kick off today,” Russell wrote, “I want to show my continued support for the players & their decision to stand against #socialinjustice. I thought about taking a new photo but was afraid I wouldn’t be able to get up this time.”

The protests began in 2016 with former 49ers quarterback Colin Kaepernick, who took a knee during the anthem to protest against police brutality and racial inequality.

Over time, many players — including Raiders quarterback Derek Carr and defensive end Khalil Mack, Eagles lineman Michael Bennett and Seahawks cornerback Jeremy Lane — joined Kaepernick’s movement.

But not everyone has been supportive of the quiet gesture during the anthem. The protests has been heavily criticized by the White House. President Donald Trump said the players are disrespecting the flag, and he’s gone so far as to call on the NFL to suspend a player for kneeling during the anthem.

During the offseason, the NFL established a new policy that requires players to stand during “The Star-Spangled Banner” on the sidelines. The NFL Players Association responded in July by filing a grievance over the league’s new policy.

Last week, all eyes were on the sidelines before the Hall of Fame game between the Bears and Ravens. The Bears stood together and linked arms during the song.