The 23-year-old has been sidelined since suffering the injury during pre-season and had recently returned to training. However, after specialist consultation, it was determined that surgery is now required to resolve the issue.
"Following specialist consultation, it has been determined the defender will undergo a surgical procedure to address the issue," Everton said in a statement. "Branthwaite will commence a structured rehabilitation programme under the supervision of the club's medical team following the operation."
The setback delays what would have been Branthwaite's first appearance of the season. The injury was initially considered minor, but complications during recovery led to this more serious intervention.
Branthwaite signed a new deal in July, committing his future to Everton until 2030. Despite not featuring this season, he was a standout performer over the past two campaigns, racking up 65 Premier League appearances and earning senior England recognition.
David Moyes urged Everton to stay on the front foot as they prepare for Saturday's Premier League meeting with Nottingham Forest at Hill Dickinson Stadium, where Sean Dyche made his first return since leaving the club nearly a year ago.
David Moyes has urged Everton to "change history" at Bournemouth tonight as they look to respond to their 4-1 home defeat to Newcastle.
Eddie Howe has urged Newcastle United to respond with purpose after their narrow Champions League setback in Marseille, insisting the squad are "still learning" but fully focused on reigniting their Premier League form at Everton on Saturday.
David Moyes said he took "real pride" in Everton's fight after Idrissa Gueye was sent off at Old Trafford, as his 10-man side battled to a remarkable 1-0 win over Manchester United.
