St Kilda is reeling after their push for finals was dealt a huge blow with Jade Gresham to spend the remainder of the season on the sidelines with a knee injury.

The Saints sit ninth on the ladder ahead of round 20, equal points with the Bulldogs who sneak into the top eight on percentage.

Gresham was subbed out in the fourth quarter of his club's 28-point win over West Coast at the weekend after falling awkwardly on his right knee.

Scans on Thursday confirmed its severity.

The 24-year-old Yorta Yorta man will require surgery, suffering a medial meniscus tear.

The setback means Gresham faces an extended period on the sidelines after club medical staff were originally hopeful the midfielder would be clear to play against Hawthorn on Saturday.

"This is a big blow for Jade, who has already had a very injury-interrupted past few years," St Kilda head of football David Rath said.

"Given Jade's history, specialists have also recommended a PCL reconstruction, so this will mean a five-month rehabilitation process."

It's a cruel end to the year for Gresham who has so far put together the best football of his seven-season career.

The midfielder averages 23 disposals, four clearances and three tackles per game in 2022.

"This is hugely disappointing for both Jade and the club, but when it comes to the long-term health of our players nothing comes above that," Rath said.

The Saints face a tough run home with games to come against top eight sides Sydney, Brisbane and ladder-leaders Geelong.

The club take on Hawthorn at Marvel Stadium on Saturday afternoon.