"Rockets already acknowledge that a period of rest 'likely measured in weeks' will be the minimum requirement before their defensive anchor is ready to the return to the lineup," the report said.
An MRI on Thursday revealed Howard has edema, or swelling due to an excess of fluids, in his knee. Howard's injury is still in the process of being evaluated, the report said.
The All-Star center has not played since Jan. 23 and has missed 16 games this season. In 32 games this season, the 29-year-old Howard has averaged 16.3 points and 11 rebounds per game.
Houston (33-15) is in second place in the NBA's Southwest Division and hosts the Chicago Bulls on Wednesday.
- Will Green