Raanta, who returned to his native Finland on Tuesday, admitted that his right ankle was opened up and cleared of the extra fluids.
"On Friday, the stitches were taken out and in one and a half weeks, I can get back to normal and start doing exercises," Raanta told IS.
Raanta, who should be more than ready for the start of training camp in September, signed a one-year, $1.4 million contract with the Blackhawks on June 3.
The 24-year-old was expected to join Helsinki IFK next season, but opted to sign with Chicago.
It's unclear when the Blackhawks became aware of Raanta's injury. Two days after signing him, the club inked veteran netminder Nikolai Khabibulin to a one-year, $2 million deal.
The Hawks did announce on June 9, though, that Raanta would not participate in on-ice drills and scrimmages during the team's prospects camp due to a "minor injury."
The native of Rauma, Finland, posted a 21-10-11 record with Assat Pori of the SM-liiga last season, with a 1.85 goals-against-average and a .943 save percentage.