The Moroccan suffered the cruciate ligament problem during Saturday's 3-1 win over Falkirk, and after assessment by club medical staff it appears his season is over.
Zemmama, 26, had only just returned from a series of niggling injuries, which had kept him out of action since 17 February.
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Hide AdThe 26-year-old playmaker has been dogged by a recurring nerve problem this season and Saturday marked his first start since 17 February.
Zemmama, who was brought to Easter Road by John Collins, missed the whole of last season after spending the 2008-09 campaign on loan to Al Sha'ab in the United Arab Emirates, due to Home Office regulations which prevented his wife obtaining a visa.