West Ham midfielder Jack Collison has been ruled out for six to seven weeks with a dislocated kneecap, the English Premier League club confirmed. He injured his right knee in the second-half of the Hammers 1-0 win against Wigan Athletic last week.
The 20-year-old underwent an exploratory operation on 10 March to discover the full extent of the injury. The player joins fellow midfielder and Swiss international Valon Behrami on the East London club's injury list.
Behrami was ruled out for six months with an anterior cruciate ligament injury in his left knee sustained against Manchester City at the start of this month.
West Ham, a revived forced under Italian manager Gianfranco Zola, are now seventh in the table. Their next match sees them at home to basement club West Bromwich Albion at Upton Park on 16 March.