Lakers reporter Mike Trudell reported the news, noting X-rays were negative.
This is a difficult setback for the 2013 All-Star, who was a bright spot for a struggling Brooklyn Nets franchise over the past few seasons and came to Los Angeles as an important part of the Lakers frontcourt.
Lopez has averaged more than 17 points per game in every season since his 2008-09 rookie campaign. He posted 20.6 points, 7.8 rebounds and 1.7 blocks per game in 2015-16 and followed with 20.5 points, 5.4 rebounds and 1.7 blocks a night last season.
Lopez was averaging 13.0 points and 4.4 rebounds per game entering play Monday in 2017-18.
Los Angeles will likely turn toward the combination of Kyle Kuzma, Julius Randle and Larry Nance Jr. in the frontcourt while Lopez is out.
While those pieces can help keep the Lakers afloat for the time being, Lopez is a veteran leader on a team looking to surprise in the Western Conference this season. They could use him back and healthy before the stretch run.