- London Olympics 2012
Greene's coach reveals surgery setback
The 400m hurdle world champion has yet to hit top form this season, his best performance more than a second slower than world leader Javier Culson.
And his coach Malcolm Arnold, who was awarded an OBE in the Queen's Birthday Honours, has revealed Greene's progress has been hampered by the setback.
"He has had a tough winter," Arnold told BBC Sport. "He didn't say much about it but he had to have some knee surgery just before Christmas which he has been rehabilitating out of since Christmas.
"He has had two races which have both been of the required Olympic A standard but not quite a quick as we had hoped for."
Greene, who is bidding to add Olympic glory to his world, European and Commonwealth golds, will compete at the GB Olympic trials in Birmingham next week and Arnold believes the Welshman is approaching peak form.
"In this last week, he has had the best weeks training I have ever seen him have," he said. "I think he is coming good at the right time."