Gera ruled out for foreseeable future
The midfielder was injured during West Brom's home defeat by Tottenham Hotspur on Saturday and will undergo further tests this week to determine the full extent of the damage.
"Zoltan is now in the hands of our excellent medical and sports science department and we just have to hope and pray that his stint on the sidelines is not an overly prolonged one," manager Roy Hodgson told the club's website.
"We still don't know for sure how long he will be out for but we know we won't be able to call on his services for the forseeable future."
Gera is in his second spell at West Brom after signing from Fulham in August.