Hoy suffered the injury after crashing in Denmark in February
Sir Chris Hoy has withdrawn from this month's cycling World Championships in Poland because of a hip injury.
The Scot picked up the problem in a crash during the keirin final at the World Cup event in Denmark in February.
He had been receiving treatment and had also modified his training programme, but has now been advised to stop riding to allow the hip enough time to heal.
He said: "I'm hugely disappointed. This is the first time I've had to miss a major championship due to injury."
The 32-year-old had avoided crashing and won all but one of the races he entered since 2006 before last month's accident.
"These things happen and it was a racing incident," he added.
"It is a miracle I have had around 30 races without a crash since I started riding the keirin.
"I'm glad it didn't happen this time last year and I'm still totally focused on being in the best shape possible for London 2012.
"This doesn't affect my long-term aim of defending my titles and I'll hopefully be back in training and competition in the near future.
"I wish the team the best of luck in Poland."
Hoy was competing competitively for the first time since the 2008 Beijing Olympics, and had only returned to serious training in January when the British squad spent four weeks in Australia.
He had been favourite to defend his two world titles in Poznan at the end of the month.
The five-time Olympic medallist had already won gold in the team sprint before his high-speed accident, which smashed his custom-made carbon fibre bike into pieces.
He was also forced to pull out of the Revolution event at the Manchester Velodrome against long-time rival Arnaud Tournant in the Frenchman's farewell race.