Blaszczykowski confirms cruciate ligament tear
The Poland international was substituted just six minutes into Dortmund's 2-2 draw with Augsburg on Saturday.
And the 28-year-old is set for a lengthy stint on the sidelines after the severity of his injury was confirmed.
"Unfortunately it is confirmed: The front knee ligaments are torn. On Thursday I have surgery," Blaszczykowski wrote on his Facebook page.
Blaszczykowski's injury is the latest in a line of setbacks in what has been a challenging campaign for Jurgen Klopp's Dortmund.
Defenders Neven Subotic and Mats Hummels have both suffered knee ligament injuries this season, while midfielder Ilkay Gundogan is close to a return to fitness following a long layoff with a back problem.
The draw with Augsburg served as another dent to Dortmund's fading title hopes, with Klopp's men now 14 points behind leaders and defending champions Bayern Munich.