The unlucky 22-year-old versatile back was carted off just four minutes into his Ulster comeback in their bonus-point 36-17 win over Cardiff Blues at the Kingspan Stadium on Friday night.
He will require surgery and will be out of rugby for up to nine months.
Ulster Rugby statement on Stuart Olding’s latest injury
It is a second serious injury to befall the twice-capped Ireland international in 2015, after he went off with ligament damage to his elbow in Ulster’s European Champions Cup match at Toulon in January.
That injury ruled the twice capped Ireland international out of Joe Schmidt’s squad for their successful RBS 6 Nations title defence earlier this month and, as with Glasgow Warriors’ Scotland international centre Alex Dunbar, Olding looks set to miss the Rugby World Cup in September.
“An MRI scan has confirmed that he has an ACL injury in his right knee,” said an Ulster Rugby statement.
“He will require surgery and will be out of rugby for up to nine months.”
The Belfast man has endured a tough start to life as a professional rugby player with a ruptured ACL in the same knee while playing for Ulster Ravens in November 2013 ruling him out of the remainder of last season.
But he returned to action with Ulster at the start of the 2014/15 PRO12 season and earned a call up to the Ireland squad for the Guinness Series, coming off the bench to score his first international try against Georgia at the Aviva Stadium.
Ulster winger Craig Gilroy was one of the first players to tweet his support for his injured colleague.
— Craig Gilroy (@cgilroy14) March 31, 2015
In better news for head coach Neil Doak, Ruan Pienaar’s arm injury is not as bad as first thought, and the South African scrum-half is expected to be available for Ulster’s PRO12 trip to the Sportsground to face Connacht on Saturday 11 April.
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