A club statement read: "Following consultations with specialists, Abou will undergo surgery to repair the injury in the near future. Abou is expected to be out for around eight to nine months.
"The thoughts and best wishes from everyone at Arsenal are with Abou, and we all wish him a successful recovery."
Diaby made 14 appearances this season and has previously endured long-term lay-offs due to ankle and thigh injuries.
Arsenal is also currently without Jack Wilshere due to a recurrence of an ankle problem that club officials fear could result in another long-term absence for the England international.