Arsenal striker Danny Welbeck has been ruled out for nine months after suffering "significant cartilage damage" to his right knee.
The news is a massive blow for Welbeck, who will miss this summer's European Championship and a large part of next season. The England international only returned to action in February this season after missing nearly 10 months with an injury to his other knee, which also needed surgery.
The latest surgery, to repair cartilage damage, will rule him out of action until next February.
Welbeck had been playing well for Arsenal, scoring five goals since his return, and was set to be included in Roy Hodgson's squad for the Euros. But the forward had to come off after just 20 minutes of Sunday's 2-2 draw at Manchester City after appearing to twist his knee when challenging for the ball.
I will be back stronger! :muscle: pic.twitter.com/ueLNSfHxZl
- Danny Welbeck (@DannyWelbeck) May 11, 2016
Welbeck underwent scans on Monday and Tuesday, and Arsenal said he underwent successful surgery on Wednesday.
"Specialists determined surgery was required after scans and tests revealed significant cartilage damage," the club said in a statement. "Danny will miss the Euro 2016 Championship in the summer and his full recovery is expected to take approximately nine months."
The club added: "Everyone at Arsenal will be working hard with Danny throughout his recovery and look forward to seeing him back on the pitch as soon as possible."
Welbeck is the second Arsenal player to be ruled out of the Euros with a knee injury after Alex Oxlade-Chamberlain extended his medial ligament in training last week.
Oxlade-Chamberlain was just returning from another knee injury suffered in February, and is expected to be sidelined until July.
Hodgson had been set to announce his squad on Thursday but pushed the date back until Monday after hearing of Welbeck's injury.
The former Manchester United forward's absence could open the door for Theo Walcott to make the squad instead, despite having struggled for playing time with Arsenal in recent months.
Both Walcott and Jack Wilshere, who is expected to be part of Hodgson's squad despite missing nearly the entire season with an ankle injury, were quick to express their sympathy on social media.