McKnight was a prolific goalscorer for Glentoran's Second XI, including scoring against the first team to seal victory in the County Antrim Shield semi-final in March 1909 and would go on to score all three goals in the final against Cliftonville .

As a more regular first team player in the 1909–10 season, McKnight scored 16 goals in 22 matches, the following season continuing to be part of the Glentoran side who won the League title as well as the City Cup and the County Antrim Shield.

[2] After scoring 23 goals in 23 games by March 1912, McKnight moved to Preston North End for a fee of £1,100, scoring his only two goals for the club in successive matches against Liverpool and Sheffield United .

[2][3] McKnight again returned to Ireland, joining Belfast Celtic and helping his side to the league title and a runners up spot in the Irish Cup in the 1914–15 season.

[4] During his spell with Nottingham Forest, McKnight was awarded a certificate of lifesaving by the Royal Humane Society[5] after saving a boy from drowning in Ardglass Harbour whilst on holiday.