Knight, making his debut for the Latics after moving from Middlesbrough on loan, received a straight red card on 39 minutes when he grabbed the ball from Carlisle striker Karl Hawley but carried it outside his penalty box.
Referee Graham Salisbury had little option but to dismiss the unlucky youngster as Hawley could have been clean through on goal but Oldham stood firm as the visitors dominated.
The Latics also had chances of their own in an absorbing game which saw all three goalkeepers make some fine saves.
Carlisle were quickly out of the traps and could have scored after four minutes when a long goal kick was picked up by Michael Bridges, who scooped it over from 18 yards.
Peter Murphy was denied by Knight after taking a long-range free-kick and midfielder Paul Murray, returning to the club he used to be captain, saw another chance blocked after finding space in the box.
Oldham's first opening came on 11 minutes as Richie Wellens burst through from a deep position and sent a shot too close to Carlisle stopper Keiren Westwood.
The Carlisle keeper then made a world-class one-handed save to his right as he somehow reached a 12-yard piledriver from Oldham's on-loan Crystal Palace striker Lewis Grabban.
The home side went even closer when teenage full-back Neal Eardley crossed from the right and Will Haining fired against the foot of the post from close range.
At the other end Kevin Gall was denied by Knight, whose game was soon to end in unfortunate circumstances.
Oldham sent on substitute keeper Terry Smith and the teenager made a brilliant stop before half-time after Simon Hackney let fly at the far post.
Smith also kept out Kevin Gray before Bridges and Hawley both wasted decent chances for the Cumbrians.
Oldham hit back on 72 minutes as another Eardley ball picked out substitute Chris Taylor for a volley which missed by inches.
They also went close in stoppage time through Andy Liddell but were happy to settle for a point.