Manchester United winger Bebe has torn his anterior cruciate ligament playing for Portugal Under-21s and could be sidelined for up to six months.
The 21-year-old is currently on loan at Turkish club Besiktas but a decision has not yet been reached on whether he will return to England for surgery.
A statement on the Besiktas website said that the two clubs would reach a "joint decision about where the operation will be done".
Bebe joined United from Vitoria de Guimaraes for £7.4m in 2010, but has played only seven first-team games for the Red Devils.
