"The last few months have been difficult for me both mentally and physically as I've come to terms with the fact that I am no longer able to compete.

"I have loved my journey in rugby. I came to England as a teenager hoping to get a few games of rugby and to see the world. I could have never predicted that one day I'd play 14 years for such a special club and go on to represent and captain England."

The New Zealand-born front-rower is England's second-most capped player of all time having made 97 appearances, behind only Jason Leonard (114). Hartley captained the Red Rose on 30 of those occasions and led them to successive Six Nations triumphs in 2016 and 2017.

At club level, Hartley is Northampton's longest-serving player, making 251 appearances in 14 years at Franklin's Gardens and winning five trophies – including Saints' only Premiership title in 2014.

Former team-mates, opponents and officials have been paying tribute on social media to the ex-Saints skipper, who was on Worcester's books before moving to Northampton in 2005.

England and Saints lock Courtney Lawes wrote: "Man I'm gonna miss running out there with you brother. Just want to say thank you for all the memories and experiences we have shared over the years. It's truly been my pleasure and honour to play beside you mate."

Chris Robshaw, who Hartley replaced as England captain in 2016, said: "Congratulations on the career @DylanHartley it's been a hell of a ride. Enjoy the next chapter."

Another former England colleague Nick Easter, the ex-Harlequins forward, added: "Congrats mate on a fantastic and colourful career. Deserve all the plaudits coming ur way. Always remember how u took ur international initiation to a new level in the '08 autumn."

Ex-England and Northampton fly-half Stephen Myler tweeted: "Congrats @DylanHartley on an unbelievable career. True leader and deserve everything you achieved in the game. Pleasure to have been alongside you for some of it."

Hartley's career, while hugely successful, was not without controversy and his disciplinary record was so poor that he accumulated 60 weeks of bans.

Among his misdemeanors were a 26-week suspension in 2007 after being cited for eye-gouging Wasps forwards Johnny O'Connor and James Haskell, while he was suspended for eight weeks in 2012 after biting the finger of Ireland's Stephen Ferris during a Six Nations clash.

The following year he was sent off for verbally abusing referee Wayne Barnes in Northampton's Premiership final loss against Leicester, earning him an 11-week ban which saw him miss the British and Irish Lions tour to Australia.

Hartley said: "My career wasn't perfect, but I wouldn't have had it any other way. I'm privileged to have experienced some amazing highs while there have also been some personal lows, all of which are powerful experiences that will stay with me forever.

"The final chapter of my career was supposed to go a different way, but that is the nature of professional sport."

Former England skipper Will Carling said: "Sorry to hear of @DylanHartley retirement from rugby due to his knee injury. Tough competitor, a great servant to England, often wrongly judged by fans & media. Good guy, good fun, bloody good captain."

Nigel Owens, considered one of the best referees of all time, said: "Very best of wishes in your retirement and congratulations on a wonderful career. On the field you were challenging at times but off the field your were a true gentleman, always pleasant and polite. Best wishes for the future."