Chalmers sustained the injury in the first quarter of Saturday's home victory against the Denver Nuggets when he landed awkwardly. He was helped off the court by Heat teammates and was scheduled to have an MRI test on Sunday.
The Heat said there was no extended damage to the knee, although Chalmers could miss as many as six of Miami's final 13 games as he recovers from the sprain. Chalmers was having one of his best stretches of an otherwise inconsistent season before the injury.
Chalmers was averaging 6.7 points, 2.4 assists and 2.2 rebounds in his third season and had started the past 28 games since he replaced Carlos Arroyo in the opening lineup on Jan. 22. Veteran point guard Mike Bibby, who signed with the Heat two weeks ago, is expected to take over for Chalmers as the starter.
The Heat could be in the market for an additional point guard, with Bibby the only healthy player at the position. Arroyo was released two weeks ago to make room for Bibby and is now with the Boston Celtics. Both LeBron James and Dwyane Wade could also handle the ball more at point guard.
The Heat, who have won five of their last six games, play at Detroit on Wednesday.
Michael Wallace covers the NBA for ESPN.com.