Speaking to BBC Radio Gloucestershire before both players had been for scans, director of rugby George Skivington said: “I don’t think either look exactly positive.”
“[It was] fairly innocuous for Max but a decent enough bang, we just hope it’s on the lesser side of it than too serious.
“But I think both of those are going to be a potentially decent enough rehab period.”
Llewellyn played in three of Wales’ four internationals last month but now joins captain Jac Morgan on the sidelines ahead of the Six Nations in eight weeks.
The 26-year-old missed two matches earlier in the campaign for Gloucester but Skivington said this was a new injury.
Versatile Joseph has played in all six of Gloucester’s Prem fixtures since signing this summer and started on the wing for their latest European match.
“[He] got his ankle caught between a couple of bodies. He’s non-weight bearing at the moment. The fact he’s on crutches probably isn’t a great sign,” Skivington added.
Gloucester are back in European action on Saturday with a trip to Munster before returning to the Prem on 19 December – away at Leicester – followed by a home fixture with Saracens on 27 December.
The Cherry and Whites do however have vice-captain Arthur Clark and Jack Clement available for the first time since the opening match of the season in a boost to their forward pack.
