Amor, 26, suffered the injury in the cup loss to Leeds last month, and there were initial fears it was a season-ending blow.
Another man injured in that defeat was Jordan Turner, who hasn’t broken his foot and the club are now saying it is just a short term ligament damage injury.
Coach Nathan Brown said: “Kyle will be out for three months with his knee which, as bad as it sounds, means he might come back and play at the end of the year. That is a bonus for us. There are hurdles to overcome but at the moment they don’t think it requires surgery.
“When Jordan’s injury was scanned we discovered it wasn’t a bone break but ligament damage. It is coming along well and it is a short term injury.”
Amor has scored two tries in seven appearances for Saints since joining from Wakefield in the close season.