1. The Catholic Wave
"Social justice" began as a Catholic concept developed in the 1840s by Father Luigi Tapparelli as an alternative to democracy and communism. Its earliest concept was a Catholic version of noblesse oblige: everyone should respect God's social hierarchy, but the rich should treat poorer people with respect and help them with charity.
In the 1930s, the antisemitic Father Charles Coughlin created the National Union for Social Justice and published a periodical titled Social Justice that attacked Jews, atheists, and Communists as the enemies of God. But Coughlin did not destroy the reputation of "social justice". Good Catholics like Dorothy Day and Father Dom Helder Camara worked hard to help the poor under that label.
This wave continues with Catholicism to the present day.
2. The Interdenominational Wave
During the 20th century, the idea of social justice spread from the Catholicism to Protestantism and Judaism. The phrase was not common in the civil rights era because it was still primarily a theological concept, but the focus in this wave began expanding from poverty to racial and gender inequality.
3. The Identitarian Wave
4. The Democratic Socialist Wave
The millennials saw that economic and social justice are entwined. This wave is so new that its differences with the third wave didn't become obvious until Clinton Democrats began trying to suppress Sanders Democrats. It's too early to know what form the fourth wave will take, but I'm optimistic. The kids are the future, no matter how hard the third wave works to defeat them.
Related: Naming the four waves of fighting racism and sexism
ETA: On Facebook, I was asked if we're now in the Antifa Wave. I answered,
It's hard for me to categorize Antifa because they're intellectually a mess, so far as I can tell. They're angry, they have no respect for their opponents, and they're obsessed with symbolic rather than practical matters, so I hope they're the last gasp of the third wave.