The Ireland centre had an operation last week after picking up a knock during Leinster's Heineken Cup Final triumph over Northampton at the end of May.
Doctors had initially hoped an operation wouldn't be needed but that assessment changed when D'Arcy failed to respond as well as hoped to treatment.
The operation appears to have been a success but D'Arcy will now be sidelined until early August.
The five to six week absence rules the 57-cap veteran out of Ireland's World Cup warm-up against Scotland at Murrayfield on August 6 but he is expected to play a part in the three remaining fixtures against France (twice) and England.
Ireland take on the French on successive weekends in Bordeaux on August 13 and Dublin on August 20 before facing Six Nations Champions England at the Aviva Stadium in their final friendly a week later.
Declan Kidney's men are currently in the first of three pre-World Cup camps, with the squad having met up at Carton House in Kildare earlier today.
D'Arcy, who was a Lion in both 2005 and 2009, won't be the only Lion missing, however, as Stephen Ferris continues his return to fitness with the Ulster coaching staff.
Ferris has been sidelined with a knee injury since January but should join D'Arcy in being fit to take part in the global gathering in New Zealand in September.