But England's interim head coach Stuart Lancaster has revealed the injury was not as bad as first feared.
"Having had a disappointing afternoon with Lee and sent him away feeling sorry for himself, the news later on in the evening was very positive," said Lancaster.
"We'll review him and see if he's fit to train. We hope he will be.
"We're very optimistic of his chances of being available this weekend."
Should Lee Dickson recover and take his place in match-day 23 would almost certainly squeeze his brother and Harlequins' scrum-half out of the squad.
Originally selected in the Saxons squad, Karl has stayed on to train with the elite player squad at their Pennyhill Park base.
He is short on match practice having only played one club game since mid-November - a 40-45 loss to the Cardiff Blues at the weekend.
The Dickson brothers have both been shoved into the limelight this Six Nations, in part, due to the absence of more established half-backs Richard Wigglesworth and Danny Care who are missing through injury and suspension respectively.