The injury occurred during Saturday's game against the Denver Nuggets, and while he continued playing, he suffered swelling overnight. He will now "undergo a period of treatment and rehabilitation" before returning.
Thompson already missed about a month with a calf strain this season, a bizarre change for someone who had been one of the most durable players in the NBA.
The Cavs big man played all 82 games in four straight seasons from 2012-16 and totaled 447 consecutive games before a thumb injury kept him out for a few games last year. He remained in the lineup virtually every night while playing significant minutes at a demanding position.
It hasn't been the same story this season, and Thompson has also failed to maintain his past production when on the court. Although he survived the team's makeover at the deadline, he is only averaging 6.3 points and 6.5 rebounds per game in 2017-18.
Unfortunately, the Cavaliers need him in the post because of a severe lack of depth down low, and his absence will be notable. Kevin Love was already out with a fractured left hand suffered in January, stretching Cleveland's frontcourt depth even thinner.
With Thompson and Love out, it will push Larry Nance Jr., Jeff Green and Ante Zizic into bigger roles in the rotation, although LeBron James will likely have to play minutes at center.