28-year-old Knaak had an outgoing contract in Rosengård after three seasons in the club. On New Year's Day, Manchester City announced that the German would be the Super League club's first January signing.
Knaak played a major role in Rosengård's successful season in Damallsvenskan, where the team won 25 out of 26 matches and only conceded nine goals. The defender was also responsible for twelve of Rosengård's 99 goals on the way to the Swedish Championship gold.
"It really helped me that I already know Therese. I really trust her and her expertise, so it gives me a good feeling. But (going to) the club was a 'no-brainer' for me," says Knaak to Manchester City's website.
City is second in the Super League and has qualified for the Champions League quarterfinals this spring.
