Neymar, who suffered the knock during PSG's Champions League win over Istanbul Basaksehir on Oct. 28, linked up with Brazil's national team before it was confirmed he wouldn't be available against Uruguay on Nov. 17.
He was already ruled out of Friday's qualifier against Venezuela prior to Thursday's announcement.
"The player trained on Monday and has since undergone intensive physiotherapy," said national team doctor Rodrigo Lasmar, as translated by Jonathan Johnson of CBS Sports.
"He performed well but not adequately for inclusive against Uruguay. When we arrived in Sao Paulo, scans had already been scheduled to monitor his response to the treatment."
It's unclear if Neymar will play for PSG when the defending Ligue 1 champions take on AS Monaco after the international break ends.