England forward Dan Ward-Smith has undergone surgery following his horrific double injury and faces a race against time to be fit for this year's World Cup.
The 29-year-old number eight was pencilled in to make his England debut in this weekend's RBS 6 Nations opener against Scotland at Twickenham, but has been ruled out for the entire tournament with the injuries suffered in Bristol's win at Northampton last Saturday.
As well as dislocating his kneecap when falling awkwardly, subsequent scans have revealed Ward-Smith also ruptured his patella tendon.
Bristol physio Paul Tompkins said: "Dan underwent surgery on Monday evening to repair the damage. I've spoken to the surgeon and he's very happy with how it went.
"Dan's obviously now facing a lengthy spell of rehab but he's a dedicated trainer and he won't shirk the hard work.
"He'll get all the best possible support to help him back towards full fitness."
Earlier this week Bristol coach Richard Hill admitted that Ward-Smith was likely to be out for six months if tests confirmed the patella tendon injury.
That would rule him out of England's two-game tour to South Africa this May and June, and raise serious questions about his ability to participate in this Autumn's World Cup.
England flanker James Haskell insists he will be pushing as hard as possible to be back from a toe injury in time to make his case for a spot in Eddie Jones' side looking to defend their RBS 6 Nations title next year.