Coach Adam Gase termed Howard as "week-to-week" with the injury.
It's a big setback for the Dolphins (6-6), who are holding on to slim playoff hopes largely because of their defensive playmakers like Howard.
"He's one of our best players, if not our best player on that side of the ball," Gase said. "We've got to make some adjustments if we have to on defense. Our guys have to step up. If he can't go, you're not going to replace him."
Howard suffered the injury during his second interception of Bills quarterback Josh Allen late in the third quarter Sunday. He missed just one snap and returned to play the fourth quarter. He didn't say anything initially to coaches or the media about the injury.
Howard was named AFC defensive player of the week for his performance against the Bills.
Gase didn't answer a question about whether Howard will need surgery, but he says he expects Howard to return this season.
Howard, a 2016 second-round pick, is having a Pro Bowl-caliber season. He leads the NFL with seven interceptions. He has three multi-interception games this season, including each of the past two games.
Patriots coach Bill Belichick raved about Howard, who had two interceptions of Tom Brady in the Dolphins' win last December, calling him "outstanding" and a "playmaker."
The Dolphins claimed cornerback Dee Delaney off waivers from the Jacksonville Jaguars Tuesday. Bobby McCain will start for Howard, and Torry McTyer and Cornell Armstrong will have to step into larger roles.