London, March 17 (IANS) Former England all-rounder Andrew Flintoff has revealed that playing in the team's victorious 2009 Ashes campaign despite a knee injury finished his international career at the age of 31.

Flintoff, who was forced to retire from all forms of cricket last September due to the persistent knee injury, said he had to endure huge amounts of pain while playing in the home series.

"I would never swap winning the Ashes but that 2009 series finished my career, my knee was in bits," Flintoff told The Wisden Cricketer magazine.

"I played through four Tests and the damage I did then has resulted in how I am now. I certainly never thought I would play my last game of cricket aged 31. I had so many injections and painkillers in my knee just to get through that series. I'm glad I did but obviously it has cost me."

The 33-year-old recently underwent an operation on his left leg to ensure he doesn't feel the pain while following his daily routine.

"I want to be able to play football with my kids or, if I wanted to, play a game of club cricket with my brother, I could do it. More than that, I just don't want to walk in pain.

"I have found myself getting quite down a couple of times in recent weeks, which is not like me at all. I am just looking forward to getting off my crutches, being able to drive again and hopefully cranking up the rehab. It is not been an easy time, though."