The 32-year-old former Crusaders front-rower had hoped rest would cure the problem, which began to affect him towards the end of last season, but coach Craig Sandercock admitted surgery became unavoidable.
"The specialist seemed to think that a bit of rest and recovery would bring it back to normal but he was in severe pain with it and the best option was to have surgery," Sandercock said. "He'll be in a boot for four weeks and after that he'll start running, so we are racing against time for him to be fit for round one."
O'Hara had the operation last week and missed the club's warm-weather training camp in Tenerife in order to undergo rehabilitation.
Two of Rovers' new signings, Sean Gleeson and Evarn Tuimavave, also missed the trip due to injury and visa issues respectively but are expected to make their debuts in the Super League opener against Catalan Dragons on Sunday, February 3.
- Sports & Recreation
- Craig Sandercock