His last appearance came from the bench against Liverpool in the Champions League quarter-final second-leg last week when the striker claimed he "couldn't run" after 24 minutes on the pitch.
It was reported that the player had visited specialist Dr Ramon Cugat in Barcelona for an exploratory surgery this week due to persistent swelling in the joint.
Aguero has scored 30 times in all competitions for newly-crowned Premier League champions City despite recently spending a month on the sidelines with a knee problem.
City's season finishes on May 13 away at Southampton, while Argentina's first game at the World Cup is against Iceland on June 16.
Sitting for too long may damage brain
To find out more, the researchers recruited 35 people who did not have dementia, aged between 45 and 75 (25 women, 10 men). This was done using the self-reported International Physical Activity Questionnaire modified for older adults (IPAQ-E).
"Recovering from an arthroscopy on my knee", the striker tweeted on Tuesday morning.
Aguero has not started a game since City's victory over Chelsea on March 4, although he was an unused substitute against Basel on March 7.
With the injury still bothering him, he was ruled out of last Saturday's 3-1 win at Tottenham, with Guardiola casting doubt over whether the forward would play again this season.
He's obviously going to work hard in a bid to be fully fit in time for the World Cup, however.