The 27-year-old was taken off at half time of his side's DFB-Pokal triumph over Eintracht Frankfurt on Saturday as Dortmund ended a run of three consecutive defeats in the final of the competition.
Initial reports suggested that Reus could miss up to six months of action as a result of the injury, but Dortmund refused to put an exact timeframe on his recovery.
"Further examinations will be conducted over the next few days to determine what course of treatment is required. With this in mind, Borussia Dortmund will not at this stage make any precise estimations as to the possible length of the player's absence," read a statement on the club's official website.
"BVB wish their DFB-Pokal hero the speediest possible recovery."
Reus has suffered an injury-plagued campaign this season, limiting him to just 17 Bundesliga appearances.