Modric has not played for Real since November after picking up the problem on international duty against Italy.
The 29-year-old is closing in on a return, though, after joining in a training session with other players who did not start in the club's 2-0 UEFA Champions League win over Schalke on Wednesday.
Modric used the club's indoor facilities as the likes of James Rodriguez, Sergio Ramos, Sami Khedira and Fabio Coentrao also continued their rehabilitation from injuries.
The ex-Tottenham midfielder did not take part in a short match at the end of training, however, preferring to sit out.
Modric moved to Real from White Hart Lane in 2012 and quickly established himself as a first-team regular.
He has made 17 appearances for the club in all competitions this season, scoring one goal.
