Ireland's Tommy Bowe will miss the Six Nations after Ulster confirmed that the centre will be out of action for up to six months.
The 31-year-old was stretchered off injured during Ireland's World Cup defeat to Argentina and his province have confirmed that he has suffered both posterior cruciate ligament and meniscal injuries in his right knee.
In a statement Ulster confirmed that Bowe went under the knife on Monday and that his recovery time will be roughly six months.
Elsewhere for Ulster, Iain Henderson has been ruled out of action for six weeks after injuring his hand while on international duty.
Henderson underwent surgery to stabilise a joint in his hand, which was also injured in the Argentina fixture, but Ulster are confident of having him back in action in December.
Jared Payne also had surgery to repair damage from Ireland's World Cup campaign.
Payne, who suffered a fractured foot, underwent a successful operation but is awaiting his first post-operative review, after which a prognosis will be known.
