Rob Gronkowski carted off field

— -- FOXBOROUGH, Mass. -- New England Patriots tight end Rob Gronkowski was carted off the field in the third quarter of Sunday's game against the Cleveland Browns after suffering what looked like a potentially serious right knee injury.

The Patriots officially have ruled Gronkowski out for the game with a leg injury.

Gronkowski hauled in a pass from Tom Brady up the seam before taking a hit directly to the knee by Browns safety T.J. Ward. Gronkowski went down to the ground, clearly in pain.

Medical personnel immediately came to Gronkowski's side, and he was eventually taken off the field on a cart. The burly tight end was unable to put weight on his right leg as he moved from the ground to the cart.

The 24-year-old Gronkowski missed the first six games of this season while recovering from offseason back and forearm surgeries. He has starred in the six games since, catching 37 passes for 560 yards and four touchdowns.

Signed to a lucrative contract extension during the 2012 offseason, Gronkowski has become a centerpiece of the Patriots. He set an NFL record for tight ends with 17 receiving touchdowns during the 2011 regular season.

There has been no official word from the team on the nature of Gronkowski's injury.