The Napoli forward was forced off at halftime in his country’s 3-2 win over Denmark, and was sent for a scan on Sunday.
The results of the scan showed Milik has ruptured the anterior cruciate ligament in his left knee, meaning a lengthy spell on the sidelines.
The striker had been off to a flying start in his career with Napoli. Since moving to Serie A from Ajax at the start of the current campaign, the 22-year-old has scored seven goals at club level in all competitions.
