The Belgium international has established himself as first choice at the Santiago Bernabeu since arriving from Chelsea in August, usurping former number one Keylor Navas after the Costa Rican started the first two LaLiga games.
Courtois has started all 16 of Madrid's LaLiga matches since and shared Champions League duty with Navas as Los Blancos qualified for the knockout stages.
For the first time since moving back to Spain he has suffered an injury, though, with no timescale put on his recovery from a hip problem.
A statement from Madrid read: "Following tests carried out on our player Thibaut Courtois today by the Real Madrid medical services, he has been diagnosed with a grade 1 injury in the left iliac muscle.
"His recovery will be monitored."