[8][9][10] Knowles played in St Helens 2020 Super League Grand Final victory over Wigan at the Kingston Communications Stadium in Hull.

[13] In the 2022 semi-final, Knowles was sent to the sin bin for a chicken wing tackle during St Helens 19-12 victory over Salford which sent the club into their fourth consecutive grand final.

Knowles and St Helens then put in a second appeal which was successful meaning he was free to play in the 2022 Super League Grand Final.

[16] On 12 April 2023, Knowles was suspended for five matches and issued a £500 fine after he was placed on report for an illegal tackle during St Helens 14-6 loss to Wigan in round 8 of the competition.

Knowles played in St Helens narrow loss against the Catalans Dragons in the semi-final which stopped them reaching a fifth successive grand final.