Retired sprint star Usain Bolt has posted medical proof to silence doubters who questioned whether he was genuinely injured during last Saturday's 4x100m relay final in London.

The 30-year-old legend pulled up during the anchor leg, as Jamaica were bidding for gold at the IAAF World Championships in his last ever race.

He spent two of the next three nights partying in the British capital, causing some to suggest that Bolt may have exaggerated the injury to excuse his rare failure.

But Bolt took to Twitter on today and shared an image - which he later deleted - of a medical scan showing a seriously torn hamstring.

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He posted it alongside the words: "Sadly I have Tear of the proximal myotendineous junction of biceps femoris in my left hamstring with partial retraction. 3 months rehab."

Eight-time Olympic champion Bolt added: "I don't usually release my medical report to the public but sadly I have sat and listened to people questioning if I was really injured.

"I have never been one to cheat my fans in anyway & my entire desire at the championship was run one last time for my fans.

"Thanks for the continued support my fans and I rest, heal and move onto the next chapter of my life."

Bolt's injury and three-month lay-off rules him out of Manchester United's charity match against Barcelona next month.

Usain Bolt posted an x-ray of his injured hamstring on Twitter
Usain Bolt posted an x-ray of his injured hamstring on Twitter

He had been due to play alongside the likes of Andy Cole, Edwin van der Sar, Paul Scholes, Jesper Blomqvist, Denis Irwin, Ronny Johnsen, Dwight Yorke, Wes Brown and Phil Neville at Old Trafford on September 2.

Bolt makes no secret of his love for the Red Devils and has been spotted at Old Trafford many times since his first visit in 2009.

He took his role as a United fan to a new level in December last year, when he called into an MUFC phone-in show to praise Jose Mourinho's men.

Playing for the famous club would have been a dream come true for Bolt, but he will now have to watch from the sidelines, as United and Barca raise money for charity.

The Manchester United Foundation made an impressive £1.8million ($NZ1.77 million) from the Legends' last two games - against Bayern Munich and Real Madrid.