The 85-year-old actor was starring as John Falstaff in a production of "Player Kings" at the Noel Coward Theatre in London's West End when he lost his footing during a fight scene.
"Following a scan, the brilliant NHS (National Health Service) team have assured us that he will make a speedy and full recovery and Ian is in good spirits," a theatre spokesperson said on Tuesday.
"The production has made the decision to cancel the performance on Tuesday June 18 so Ian can rest."
He is expected to return to the stage on Wednesday.
McKellen, who also played "Magneto" in the X-Men films, is one of Britain’s most recognised actors, having won many awards during a 60-year career on stage and screen.
"Player Kings" is a return to Shakespeare for McKellen, combining two of the Bard's history plays about King Henry IV.
