The New Zealand defender missed the Hammers' weekend defeat at Norwich City, having previously started every league game for the club this season.
The influential 25-year-old has admitted that his problem is 'serious' and it has definitely ruled him out of his country's massive World Cup qualifying double header with Mexico this month.
"There's maybe a one per cent chance, if a miracle happens, but apart from that the injury is serious enough that it's going to take a far longer time than two weeks," Reid confirmed to New Zealand based Radio Live.
Reid also tweeted to say he was 'devastated' to be missing games for both club and country.
Reports claim that Reid could be looking at more than two months on the sidelines, but West Ham insist that they are still 'assessing' the injury.
After the Norwich game, West Ham boss Sam Allardyce insisted that despite the loss, Reid's absence was not a problem.
"I can't see too much that James Tomkins and James Collins did wrong. I thought they were extremely solid at the back," he said.
"We didn't miss Winston Reid as I thought they were very good and from a defensive point of view they didn't deserve to concede three goals.
"The third goal came when we threw everybody forward so we were either going to get a 2-2 or they were going to sneak one, which they did. Snodgrass has hit a brilliant free-kick over the wall into the net. You can't fault the wall or the goalkeeper when they put them in that area."