Middlesbrough boss Gareth Southgate admits striker Mido will be missing until the New Year.
Southgate told the club's official website: "We were recommended to try a course of injections but unfortunately these have failed to improve his symptoms.
"Due to the nature of the injury, it's very difficult to put a timescale on it but what Mido needs to do now is rest from playing football or training with the team.
"The aim of the rehabilitation during this period will be to strengthen the areas around the injury and in particular work on his core stability.
"Our medical team will work closely with him over the weeks ahead to ensure we eventually have him back fit and raring to go."
But the under-pressure boss accepts the 24-year-old former Tottenham striker is unlikely to play again in 2007.
Southgate added: "It is frustrating for Mido and for the rest of us to lose him in this way because we all want him out on the pitch and scoring goals.
"But the most important thing is that we resolve the problem even if it unfortunately takes longer than we would like."