Liverpool players took a knee around the centre circle at Anfield in a message of support following the death in police custody of African-American George Floyd in Minneapolis.
The picture featuring 29 Reds players came with the caption “Unity is strength. #BlackLivesMatter”.
Players reportedly requested the picture during training on Monday.
Manchester United’s Paul Pogba and Marcus Rashford added their voices to worldwide protests against racism.
Protests have been held after Floyd, an unarmed black man, died on 25 May after being restrained by white Minneapolis police officer Derek Chauvin, who kneeled on his neck for almost nine minutes to pin him down.
Chauvin has since been charged with his murder and sacked.
Kaepernick first protested against racial injustice and police brutality by kneeling down during the United States national anthem in the summer of 2016. Since then, that gesture has become symbolic to the Black Lives Matter movement.
United midfielder and France World Cup winner Pogba said he felt “felt anger, pity, hatred, indignation, pain and sadness” in a passionate Instagram post.
He added: “Sadness for George and for all black people who suffer from racism EVERY DAY! Whether in football, at work, at school, ANYWHERE! This has to stop, once and for all. Not tomorrow or the next day, it has to end TODAY!
“Violent acts of racism can no longer be tolerated. I can’t tolerate, I won’t tolerate, WE WON’T TOLERATE.
“Racism is ignorance, LOVE is intelligence, STOP the silence, STOP racism.”
United team-mate and England footballer Rashford said he had been “trying to process what is going on in the world”.
He added: “At a time I’ve been asking people to come together, work together and be united, we appear to be more divided than ever.
“People are hurting and people need answers. Black lives matter. Black culture matters. Black communities matter. We matter.”