"Sad news," Gold wrote on his official Twitter handle. (@davidgold) "Ayew has injured his quadriceps and will need surgery.
"He will be out for four months. Good luck Andre."
The Ghana international joined for a club record fee of 20.5 million pounds ($26.71 million) from Swansea City earlier this month, having scored 12 goals in 34 Premier League outings last season.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Stijn Vandenbroucke, the club's head of medical and sports science, told West Ham's website on Wednesday that the forward faced a "significant rehabilitation period." (www.whufc.com)
West Ham, who finished seventh last season, will play their first league game at their new London Stadium home on Sunday when they host Bournemouth.
(Reporting by Ed Dove; editing by Clare Lovell)
