Thus, the season is likely over for Arsenal's Brazilian striker.
"Gabby will undergo surgery in the coming days and then begin his recovery and rehabilitation," writes Arsenal.
Coach Mikel Arteta commented on Gabriel Jesus' status before the final examination was made on Tuesday and said:
We know more now, and it doesn't look good at all. We were very worried after the match, and we are very worried today.
The injury comes at an inconvenient time for the league's second-place team. Partly due to the Brazilian's top form with six goals in as many matches before the meeting with United, partly because a match against London rival Tottenham awaits on Wednesday.