Ramos limped off the field on Wednesday in the eighth minute of the hard-fought Spanish league clash against Sevilla that Madrid edged 2-1.
The 28-year-old Ramos went for exams at the Sanitas clinic in the Madrid suburb of La Moraleja early Friday looking serious, and saying "Here we go," as he entered the building.
Madrid confirmed the exam results in a statement later. Ramos will miss the derby against Atletico Madrid on Saturday, and up five other matches. He should be fully recovered for the next clasico against Barcelona in late March.
To add to Madrid's woes, Spain's sports tribunal on Friday upheld the football federation's one-match ban on Brazil defender Marcelo, meaning the European champion will be without three of its first-choice defenders for the derby, as Pepe is also out with a rib injury.