Reid has successful surgery on ankle
Reid had been an ever-present in the club's Premier League campaign before sustaining the injury in training earlier this month.
While no time scale has been set for his return to action, West Ham's head of sports science and sports medicine, Andy Rolls, confirmed the surgery went according to plan.
"Winston had an operation on his ankle injury to stabilise the joint. This procedure went well," he told the club's official website.
"He will now convalesce for a few days before starting his rehabilitation."
The New Zealand international has made 92 appearances for the club since joining in 2010 from Danish side FC Midtjylland.