Flintoff has said there is a possibility he might be unable to play again
Former England Test all-rounder Andrew Flintoff has suffered a complication following surgery on his injured knee.
After bowing out of Test cricket after England's Ashes win, the 31-year-old Flintoff had surgery, but now his right calf has minor deep vein thrombosis.
An England and Wales Cricket Board statement read: "This will require a simple course of treatment and will not complicate his recovery from surgery."
No timescale has been given for a possible return to action for Flintoff.
But he is expected to be sidelined for a minimum of six months.
Flintoff signed off his Test career by helping England reclaim the Ashes from Australia, courtesy of a 197-run victory at The Oval which clinched the series 2-1.
He is still committed to representing his country in one-day and Twenty20 internationals, but recently revealed there was a possibility he might be unable to play again.
"You don't want any complications, an operation like that is a big enough tribulation as it is," said England captain Andrew Straus after Australia's second one-day international victory on Sunday.
"I just feel for him because he's got a lot of rehab ahead of him, and you don't want it to be slowed down in any way. Hopefully, it all will all go according to plan from here on."
Former Australia captain Steve Waugh suffered a deep vein thrombosis in his right leg after tearing a calf muscle during the 2001 Ashes series in England but made a full recovery and was able to continue his international career.