Moreno fell awkwardly on his arm after his first carry and was ruled out for the rest of the game.
Driving up the middle for a 4-yard gain, Moreno was initially hit on the right side by safety Nickell Robey. Linebacker Nigel Bradham then struck Moreno from the left, hitting him directly in the arm.
Moreno immediately clutched his left forearm as he lay on the field. He was attended to by trainers and then escorted to the locker room.
"I just seen him on the ground. I know it wasn't good because he never really stays on the ground like that," Dolphins wide receiver Mike Wallace said. "It was quiet for a little while, but it was early in the game and we had to keep playing. We definitely missed his intensity."
Moreno was crucial in last Sunday's 33-20 victory against the New England Patriots. He rushed for 134 yards and a touchdown, and led all NFL rushers after Week 1.
"Obviously, we'd love to have him, but you have to deal with those things," Dolphins coach Joe Philbin said. "They pop up in football. Injuries happen. So it didn't really impact the game plan. Other guys have to step up. That's football. If a guy gets injured you can't really alter things."
The Dolphins signed Moreno to a one-year, $3 million contract this offseason.
The Associated Press contributed to this report.