Over the past weeks, the Egypt forward was nursing a knee injury in his homeland as he was resolving problems related to his mandatory military service.

After finishing the required paperwork, Zidan issued a travel clearance and flew back to Germany.

"I am so happy that now everything is settled," he was quoted as saying by Bild.

Zidan has been ruled out of action since April when he sustained a serious cruciate ligament injury in Dortmund's 1-1 draw with Hoffenheim.

The 28-year-old should return to action either in October or November.

"I've only seen the start of the season on the internet and that was the maximum penalty," said Zidan.

Former Hamburg man Zidan, who forms a productive partnership with Paraguayan striker Lucas Barrios upfront at Signal Iduna Park, scored six Bundesliga goals and dished out many assists last season.