Rob Gronkowski scared the hell out of New England Patriots fans last night ... when the superstar tight end BODY SLAMMED his friend on stage at a Las Vegas nightclub ... landing hard on his broken forearm ... and TMZ has the footage.
Gronkowski -- who signed a $54 million six-year contract extension in June -- broke his forearm last season, then injured it again during the Pats' first playoff game against the Texans.
But that didn't stop him from executing a Stone Cold Stunner-esque move on a friend during a playful dance battle at XS nightclub last night.
As Gronkowski was throwing his friend to the ground, the tight end -- who was wearing a protective sleeve on his busted wing -- also crashed to the ground and smacked his damaged arm on the stage in the process.
In fact, we gotta ask ...