Former England captain Dylan Hartley says he felt "fraudulent" being sidelined by a long-term knee injury that eventually led to his retirement.

The ex-Northampton hooker called time on his career this month, having not played since December 2018.

Hartley, 33, says he hoped to return for the World Cup in Japan and got "worn down" by having to keep delaying his comeback from injury.

"I got sick of saying the same old line," said Hartley

"People were asking 'when are you going to play again?' and I was going 'err, about six weeks'. Two weeks later someone asks and I say 'about six weeks'.

"In the end I just got worn down by it and realised I had probably had enough. So I just called it."

Hartley, who won 97 Test caps and played 251 times for Northampton over 14 seasons, injured his knee in a mach against Worcester Warriors on 21 December last year.

"Once that World Cup dream went out the window and I wasn't getting the progress from my knee I wanted, I was thinking 'why do I keep pressing to play a handful of games for Northampton?'" he told the Rugby Union Weekly podcast.

"I couldn't put a return date on it. You start feeling fraudulent.

"I was thinking I needed to play pretty soon and couldn't see myself playing within the next month or so."

Hartley, who skippered England to a Six Nations Grand Slam in 2016 and won the Six Nations again the following year, says the decision to retire was a "weight off the shoulders".

He is currently working with the hookers at Northampton and helping to mentor players, and says he has thought about careers in coaching or the media.

"It's liberating," he added. "I am having a bit of down time. Christmas is something we don't know how to enjoy as players.

"I would like to have some time away from it all and think about what I want to do."