Hannah Southwell's NRLW season is over as quick as it began following confirmation of an ACL tear for the Newcastle Knights' lock forward.

A former Dragon and Rooster in the NRLW, Southwell hails from Newcastle originally, debuting for the Knights in the same game that 17-year-old sister Jess made her NRLW debut at halfback.

The lock slipped awkwardly during the game against the Broncos, allaying fears of an ACL tear after stunningly playing on for 20 minutes, however scans on Tuesday confirmed the worst for the local product.

Southwell was one of a number of star recruits nabbed by the Knights for this season, joined by Origin stars Millie Boyle and Tamika Upton in the starting side, however the superstars would only combine for 33 minutes before Southwell's season was over.

The injury cruels what would've been an incredibly special night for Hannah.

Her final game for the Newcastle Jets came against the Brisbane Roar at McDonald Jones Stadium, capping off the symmetry by playing her maiden Knights game against the Brisbane Broncos - at McDonald Jones Stadium.

It was the first game she has played with sister Jess at the elite level - something the duo is certain to sure in the coming years, when Hannah returns to the playing field.

The NRL physio says the injury is a lot more common in female sports, and will take up to three-quarters of a year to fully heal.

The ACL injury will also throw a spanner into the works for the Jillaroos, especially seeing as Southwell was regarded a short-priced favourite to don the green and gold this October.

The Knights sit second on the NRLW ladder by a converted try, the Sydney Roosters' thumping of Parramatta ensuring the reigning premiers start the season on top of the table.

Newcastle's NRLW side will face off against the Gold Coast Titans at CBus Super Stadium on Sunday night, naming Simone Karpani at lock in lieu of Southwell.