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.
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.
The Dolphins signed Moreno to a one-year, $3 million contract this offseason.
The Associated Press contributed to this report.