The 23-year-old is edging closer to his comeback, but has stated he will still need time before he is back to his normal physical self
The Germany international has not featured for BVB since their Bundesliga opener against Augsburg in August, but recently resumed squad training again.
Nevertheless, Gundogan - who has been told by the club to make a decision over his future sooner rather than later after entering the last 18 months of his contract - has made it clear that his physical problems are not over just yet.
"I'm still having pain," Gundogan was quoted as saying by Bild.
"The things that I've been doing so far are going fine, but there will be moments where I will have to get used to the intense work again.
"I am not top fit just yet and I'm not completely pain free at the moment. I still have pain in my hip, calf and shin.
"My main objective is to get fully healthy again. Once I've achieved that, I want to give my all again."
Dortmund resume Bundesliga action at home against Augsburg on January 25.