Taumalolo limped off after his opening hit-up of the contest and will miss up to eight weeks with a grade three medial strain.
Paul Green's men were also forced to win without hooker Jake Granville who left the field in the seventh minute and didn't return with a concussion.
The visitors' disastrous start continued when Chris Houston score the opening try of the contest in the 14th minute but the Cowboys answered with three tries before the break to lead 16-6.
North Queensland continued the onslaught almost immediately after the resumption when Justin O'Neill scored his second try.
Akuila Uate answered for the Knights with a brilliant solo try before Michael Morgan crossed to restore the Cowboys' 14-point buffer.
The Knights weren't finished, scoring tries off consecutive sets to get within two points but they couldn't land the killer blow in a tense finish to slump to their fourth straight loss.
