Justin Bieber Gets His Back Cracked by Patrick Schwarzenegger

Justin Bieber can certainly afford a chiropractor, but in a pinch an actor/model will do.

Patrick Schwarzenegger gave the Biebs a lift on the streets of New York City Saturday, and it looks like they went virtually unnoticed.

In all fairness ... they were actually in SoHo, where it's super uncool to gawk at celebs.

The boyz know each other from L.A. and it's not the first time they've hung out together.

Bieber's got some downtime ... he's in the middle of his "Purpose" tour.