The Portuguese winger is looking at a six-month lay-off, the club have confirmed...
The Portuguese international caught his studs in the turf early on in the Hammers' Asia Trophy defeat by Tottenham Hotspur earlier today in Beijing, and the 31-year-old will now await further tests, once the swelling on the injury has subsided, to see if he requires surgery.
A Jermain Defoe strike meant that Spurs won the London derby 1-0, and Irons' boss Gianfranco Zola felt that his team were a little short on fitness, as well being affected by Boa Morte's injury.
"I am really sorry for him [Boa Morte]," Zola told the club's official website. "I think certainly the injury was one of the problems but physically we need to catch up a little bit.
"We talked about the forward positions already last season. We need to improve that part. We are working on that. Obviously when you are at the beginning of the pre-season and you lack a little bit of condition you notice it the most in attack.
"It is easy to have problems going forward because you need to be sharp and quick.
"Right now we are not sharp and quick but it is something that we knew about and it is not going to be a problem. We are going to sort it out."
The Hammers will now face Chinese outfit Beijing Guoan, beaten by Hull City today on penalties, in Friday's third place play-off, and Zola is hoping for an improvement then.
"We were not as good as we could be but it is the first real match we played," he added. "We have worked hard so it is understandable. The conditions are there for us and for the opposition as well so I don't think it is that. We have worked very hard and this was the first real match for us.
"I am going to use it as a good game to see the problems and to work on them. I take it in a positive way."
Zack Wilson, Goal.com