Initial reports from Wasps' medical team suggested the scrum-half would be ruled out for a month, but further assessment has seen the England hopeful sidelined until January 2019.
Robson, 26, was forced from the field during Wasps' home defeat to his former side Gloucester last weekend, replaced by substitute half-back Craig Hampson a minute before the half-time break.
Wasps confirmed Robson's three-month layoff when announcing their side to face European champions Leinster tomorrow evening.
Robson's 2019 return will see the attack-minded scrum-half ruled out of a chance to feature in England/s Autumn Internationals campaign last month, having been included in consecutive training camps since touring South Africa last June.
Wasps will turn to Joe Simpson and Hampson to fill the void, proving no shortage in strength in depth in the nine jersey.
England head coach Eddie Jones is likely to employ the familiar pairing of Leicester's Ben Youngs and Harlequins' Danny Care, with Saracens man Ben Spencer snapping at the hells of the latter.