The 21-year-old has sustained a raptured anterior cruciate ligament injury in his right knee.
Okore joined Villa in a £4million deal from FC Nordsjaelland.
A club statement read: “Following clinical examination and the results of an MRI scan, the club can confirm that Jores Okore sustained a ruptured anterior cruciate ligament injury in his right knee in the game against Newcastle on Saturday.
“Jores will undergo surgery in due course and he could be sidelined for a period of up to nine months.”
