The Northern Ireland Under-21 international will wear the number 28 shirt and was on the bench for Saturday's trip to Leyton Orient.
McKnight, 20, started out as a trainee at Barnsley without making any first team appearances.
He joined Shrewsbury last summer, but was released in January.
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League Two side Morecambe have signed former Shrewsbury midfielder Darren McKnight on a short-term deal until the end of the season.