Grandison was initially ruled out for up to six weeks with the problem which forced him to be replaced at half-time against Swindon on January 19.
He has spent the last fortnight working closely with physio Chris Skitt and manager Graham Turner feels the former Coventry trainee is making good progress.
"Earlier this morning (Tuesday) he reported to a hospital down in Cambridge. They'll put him out and inject him and Chris Skitt will pick him up later to bring him back to the midlands," Turner told the club's official website.
"We're hoping that it will all go well for him. After this it's another fortnight's rest and then we'll take stock of how he is and decide on where he goes from there.
"It was always going to be a couple of weeks rest, then an injection followed by another couple of weeks of rest to see how it all settles down and see whether we can move it forward from there rather than the requirement of surgery."
- Sports & Recreation
- Graham Turner