Oxlade-Chamberlain suffered a lower leg injury during England's friendly against Ecuador in Miami, putting his tournament participation in doubt
Manager Roy Hodgson is concerned about the injury sustained in a tackle with Carlos Gruezo, just days before England open their campaign against Italy.
He was quickly taken off and Hodgson admitted at his post-match press conference that he was worried about the youngster who also missed the end of the Premier League season with a groin injury.
Oxlade-Chamberlain was noticeably limping as he left the England dressing room and headed through the media mixed zone on his way out of Sun Life Stadium.
Hodgson said: "Oxlade-Chamberlain is the one that bothers me. His knee buckled under the the challenge as the player turned into him.
"He'll have a scan. When we've had the scan, we'll know more."
The England coach also confirmed Jack Wilshere and Luke Shaw were taken off in the second half as a precaution.
"It was cramp. We took them off for those reasons alone," he added.
Despite the injury concerns, Hodgson was pleased with the performances of his players, especially those of experienced duo Wayne Rooney and Frank Lampard.
"Rooney and Lampard I thought were immense," he said. "It's hot out there, they have got a lot of young players around them and I thought they really showed their maturity and we saw the benefit of that.
"That proves to me as well that we have a balance between experience and youth and I shall go away from today's game relatively happy.
"It would have been nice to win it but certainly there were many positives I can take from it.
"I thought it was a very good game. I was disappointed with the sendings off, and the potential injury to one of our players - but as a friendly, a warm-up match for our players, it was good.
"They tested us but we dealt with them very well for long periods, and caused their defence many problems. We could have been several goals up before they scored their goal."
Hodgson also played down Raheem Sterling's dismissal against Ecuador.
The Liverpool winger was sent off for a reckless challenge on Antonio Valencia and will be suspended for England's friendly against Honduras on Saturday.
The 19-year-old, though, will be able to play in the Three Lions' opening World Cup game against Italy on June 14.
"I'm disappointed," said Hodgson. "I thought it was a fierce challenge from young Raheem, not a foul challenge. He played the ball.
"I'm disappointed with Antonio's reaction, grabbing the player. Had he not jumped up there wouldn't have been a problem but, when he does that, the referee had to deal with that and sent Raheem off.
"I'm pleased Raheem didn't react to a lot of people milling around him."