West Ham United have confirmed midfielder Valon Behrami is expected to be out for six months with an anterior cruciate ligament injury in his left knee.
Switzerland international Behrami was stretchered off in the recent 1-0 win over Manchester City after twisting his ankle and knee.
Speaking after sustaining the injury, Behrami said that he expected to miss the rest of the season.
A statement on the club's official website read: "Behrami underwent keyhole surgery in Italy to assess and then repair the damage on Tuesday after two previous MRI scans.
"Behrami is due back in London next week, where he will begin his rehabilitation with the club's medical staff as soon as possible."
The news is a blow to the Hammers after Behrami had impressed since signing at Upton Park from Lazio last summer.