The 31-year-old was stretchered off during his side's 4-3 Scottish Premiership defeat at St Mirren Park on Saturday and the club were concerned he had suffered cruciate ligament damage.
Manager Tommy Wright told the club's official website: "The good news this morning is that the consultant has reported no damage to his cruciate and at this stage we just have to let the knee settle and then give him rehab.
"Steven's absence will be weeks in length rather than what we first feared - a season-ending injury - but it is still clearly a big blow for the player and the club."
Meanwhile, Saints reported that they were "trying to move forward to secure the services" of 31-year-old Bosnia centre-back Sanel Jahic, who has been on trial with the club.
With Steven Anderson out until the turn of the year with a dislocated thumb, Tommy Wright had already been keen to sign a central defender before Frazer Wright was sent off against the Buddies, ensuring he is suspended for the visit of Motherwell on Sunday.